Conjugates for treating diseases

ABSTRACT

The present disclosure relates to pyrrolobenzodiazepine (PBD) prodrugs and conjugates thereof. The present disclosure also relates to pharmaceutical compositions of the conjugates described herein, methods of making and methods of using the same.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is continuation of U.S. application Ser. No. 15/557,703filed on Sep. 12, 2017, which is a U.S. national stage application under35 U.S.C. § 371(b) of International Application No. PCT/US2015/020397filed Mar. 13, 2015, the disclosure of which is hereby incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates to pyrrolobenzodiazepine (PBD) prodrugsand conjugates thereof. The present disclosure also relates topharmaceutical compositions of the conjugates described herein, methodsof making and methods of using the same.

BACKGROUND

The mammalian immune system provides a means for the recognition andelimination of pathogenic cells, such as tumor cells, and other invadingforeign pathogens. While the immune system normally provides a strongline of defense, there are many instances where pathogenic cells, suchas cancer cells, and other infectious agents evade a host immuneresponse and proliferate or persist with concomitant host pathogenicity.Chemotherapeutic agents and radiation therapies have been developed toeliminate, for example, replicating neoplasms. However, many of thecurrently available chemotherapeutic agents and radiation therapyregimens have adverse side effects because they lack sufficientselectivity to preferentially destroy pathogenic cells, and therefore,may also harm normal host cells, such as cells of the hematopoieticsystem, and other non-pathogenic cells. The adverse side effects ofthese anticancer drugs highlight the need for the development of newtherapies selective for pathogenic cell populations and with reducedhost toxicity.

Researchers have developed therapeutic protocols for destroyingpathogenic cells by targeting cytotoxic compounds to such cells. Many ofthese protocols utilize toxins conjugated to antibodies that bind toantigens unique to or overexpressed by the pathogenic cells in anattempt to minimize delivery of the toxin to normal cells. Using thisapproach, certain immunotoxins have been developed consisting ofantibodies directed to specific antigens on pathogenic cells, theantibodies being linked to toxins such as ricin, Pseudomonas exotoxin,Diptheria toxin, and tumor necrosis factor. These immunotoxins targetpathogenic cells, such as tumor cells, bearing the specific antigensrecognized by the antibody (Olsnes, S., Immunol. Today, 10, pp. 291-295,1989; Melby, E. L., Cancer Res., 53(8), pp. 1755-1760, 1993; Better, M.D., PCT Publication Number WO 91/07418, published May 30, 1991).

Another approach for targeting populations of pathogenic cells, such ascancer cells or foreign pathogens, in a host is to enhance the hostimmune response against the pathogenic cells to avoid the need foradministration of compounds that may also exhibit independent hosttoxicity. One reported strategy for immunotherapy is to bind antibodies,for example, genetically engineered multimeric antibodies, to thesurface of tumor cells to display the constant region of the antibodieson the cell surface and thereby induce tumor cell killing by variousimmune-system mediated processes (De Vita, V. T., Biologic Therapy ofCancer, 2d ed. Philadelphia, Lippincott, 1995; Soulillou, J. P., U.S.Pat. No. 5,672,486). However, these approaches have been complicated bythe difficulties in defining tumor-specific antigens.

Folate plays important roles in nucleotide biosynthesis and celldivision, intracellular activities which occur in both malignant andcertain normal cells. The folate receptor has a high affinity forfolate, which, upon binding the folate receptor, impacts the cell cyclein dividing cells. As a result, folate receptors have been implicated ina variety of cancers (e.g., ovarian, endometrial, lung and breast) whichhave been shown to demonstrate high folate receptor expression. Incontrast, folate receptor expression in normal tissues is limited (e.g.,kidney, liver, intestines and placenta). This differential expression ofthe folate receptor in neoplastic and normal tissues makes the folatereceptor an ideal target for small molecule drug development. Thedevelopment of folate conjugates represents one avenue for the discoveryof new treatments that take advantage of differential expression of thefolate receptor. There is a great need for the development of folateconjugates, methods to identify folate receptor positive cancers, andmethods to treat patients with folate receptor positive cancers.

SUMMARY

In one aspect, the present disclosure provides conjugates comprising abinding ligand, a linker and a drug, having the formulaB-(AA)_(z1)-L²-(L³)_(z2)-(AA)_(z3)-(L¹)_(z4)-(L⁴)_(z5)-D¹-L⁵-D²,B-(AA)_(z10)-L²-D², B-(AA)_(z11)-L²-D¹-L⁵-D¹-L²-(AA)_(z12)-B orB-L¹-AA-L¹-AA-L¹-L²-(L³)_(z6)-(L⁴)_(z7)-(AA)_(z8)-(L⁴)_(z9)-D¹-L⁵-D²,

wherein each of B, AA, L¹, L², L³, L⁴, L⁵, D¹, D², z1, z2, z3, z4, z5,z6, z7, z8, z9, z10, z11 and z12 are defined as described herein; or apharmaceutically acceptable salt thereof.

In another aspect, the disclosure provides pharmaceutical compositionscomprising a therapeutically effective amount of the conjugatesdescribed herein, or a pharmaceutically acceptable salt thereof, and atleast on excipient.

In another aspect, the disclosure provides a method of treating abnormalcell growth in a mammal, including a human, the method comprisingadministering to the mammal any of the conjugates or compositionsdescribed herein.

The conjugates of the present disclosure can be described as embodimentsin any of the following enumerated clauses. It will be understood thatany of the embodiments described herein can be used in connection withany other embodiments described herein to the extent that theembodiments do not contradict one another.

1. A conjugate comprising a binding ligand, a linker and a drug, havingthe formulaB-(AA)_(z1)-L²-(L³)_(z2)-(AA)_(z3)-(L¹)_(z4)-(L⁴)_(z5)-D¹-L-D²,B-(AA)_(z10)-L²-D², B-(AA)_(z11)-L²-D¹-L⁵-D¹-L²-(AA)_(z12)-B orB-L¹-AA-L¹-AA-L¹-L²-(L³)_(z6)-(L⁴)_(z7)-(AA)_(z8)-(L⁴)_(z9)-D¹-L-D²,wherein

each z1, z10, z11 and z12 is each independently 2, 3, 4 or 5;

z2 is 0, 1 or 2;

z3 is 0, 1, 2, 3 or 4;

z4 is 0, 1 or 2; and

z5 is 0, 1 or 2

z6 is 0, 1 or 2;

z7 is 0, 1 or 2;

z8 is 0, 1, 2, 3 or 4;

z9 is 0, 1 or 2;

B is of the formula I

wherein

R¹ and R² in each instance are independently selected from the groupconsisting of H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,—OR⁷, —SR⁷ and —NR⁷R^(7′), wherein each hydrogen atom in C₁-C₆ alkyl,C₂-C₆ alkenyl and C₂-C₆ alkynyl is independently optionally substitutedby halogen, —OR⁸, —SR⁸, —NR⁸R^(8′), —C(O)R⁸, —C(O)OR⁸ or —C(O)NR⁸R^(8′);

R³, R⁴, R⁵ and R⁶ are each independently selected from the groupconsisting of H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,—CN, —NO₂, —NCO, —OR⁹, —SR⁹, —NR⁹R^(9′), —C(O)R⁹, —C(O)OR⁹ and—C(O)NR⁹R^(9′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyland C₂-C₆ alkynyl is independently optionally substituted by halogen,—OR¹⁰, —SR¹⁰, —NR¹⁰R^(10′), —C(O)R¹⁰, —C(O)OR¹⁰ or —C(O)NR¹⁰R^(10′);

each R⁷, R^(7′), R⁸, R^(8′), R⁹, R^(9′), R¹⁰ and R^(10′) isindependently H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl or C₂-C₆ alkynyl;

X¹ is —NR¹¹—, ═N—, —N═, —C(R¹¹)═ or ═C(R¹¹)—;

X² is —NR^(11′)— or ═N—;

X³ is —NR^(11″)—, —N═ or —C(R^(11′))═;

X⁴ is —N═ or —C═;

X⁵ is NR¹² or CR¹²R^(12′);

Y¹ is H, D, —OR¹³, —SR¹³ or —NR¹³R^(13′) when X¹ is —N═ or —C(R¹¹)═, orY¹ is ═O when X¹ is —NR¹¹—, ═N— or ═C(R¹¹)—;

Y² is H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, —C(O)R¹⁴, —C(O)OR¹⁴,—C(O)NR¹⁴R^(14′) when X⁴ is —C═, or Y² is absent when X⁴ is —N═;

R¹¹, R^(11′), R^(11″), R¹², R^(12′), R¹³, R^(13′), R¹⁴ and R^(14′) areeach independently selected from the group consisting of H, D, C₁-C₆alkyl, —C(O)R¹⁵, —C(O)OR¹⁵ and —C(O)NR¹⁵R^(15′);

R¹⁵ and R^(15′) are each independently H or C₁-C₆ alkyl;

m is 1, 2, 3 or 4;

AA is an amino acid;

L¹ is a linker of the formula II

wherein

R¹⁶ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, —C(O)R¹⁹, —C(O)OR¹⁹ and —C(O)NR¹⁹R^(19′),wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl and C₂-C₆alkynyl is independently optionally substituted by halogen, C₁-C₆ alkyl,C₂-C₆ alkenyl, and C₂-C₆ alkynyl, —OR²⁰, —OC(O)R²⁰, —OC(O)NR²⁰R^(20′),—OS(O)R²⁰, —OS(O)₂R²⁰, —SR²⁰, —S(O)R²⁰, —S(O)₂R²⁰, —S(O)NR²⁰R^(20′),—S(O)₂NR²⁰R^(20′), —OS(O)NR²⁰R^(20′), —OS(O)₂NR²⁰R^(20′), —NR²⁰R^(20′),—NR²⁰C(O)R²¹, —NR²⁰C(O)OR²¹, —NR²⁰C(O)NR²¹R^(21′), —NR²⁰S(O)R²¹,—NR²⁰S(O)₂R²¹, —NR²⁰S(O)NR²¹R^(21′), —NR²⁰S(O)₂NR²¹R^(21′), —C(O)R²⁰,—C(O)OR²⁰ or —C(O)NR²⁰R^(20′);

each R¹⁷ and R^(17′) is independently selected from the group consistingof H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR²², —OC(O)R²², —OC(O)NR²²R^(22′), —OS(O)R²²,—OS(O)₂R²², —SR²², —S(O)R²², —S(O)₂R²², —S(O)NR²²R^(22′),—S(O)₂NR²²R^(22′), —OS(O)NR²²R^(22′), —OS(O)₂NR²²R^(22′), —NR²²R^(22′),—NR²²C(O)R²³, —NR²²C(O)OR²³, —NR²²C(O)NR²³R^(23′), —NR²²S(O)R²³,—NR²²S(O)₂R²³, —NR²²S(O)NR²³R^(23′), —NR²²S(O)₂NR²³R^(23′), —C(O)R²²,—C(O)OR²², and —C(O)NR²²R^(22′), wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, —OR²⁴, —OC(O)R²⁴, —OC(O)NR²⁴R^(24′), —OS(O)R²⁴,—OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴, —S(O)₂R²⁴, —S(O)NR²⁴R^(24′),—S(O)₂NR²⁴R^(24′), —OS(O)NR²⁴R^(24′), —OS(O)₂NR²⁴R^(24′), —NR²⁴R^(24′),—NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵, —NR²⁴C(O)NR²⁵R^(25′), —NR²⁴S(O)R²⁵,—NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^(25′), —NR²⁴S(O)₂NR²⁵R^(25′), —C(O)R²⁴,—C(O)OR²⁴ or —C(O)NR²⁴R^(24′); or R¹⁷ and R^(17′) may combine to form aC₄-C₆ cycloalkyl or a 4- to 6-membered heterocycle, wherein eachhydrogen atom in C₄-C₆ cycloalkyl or 4- to 6-membered heterocycle isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR²⁴,—OC(O)R²⁴, —OC(O)NR²⁴R^(24′), —OS(O)R²⁴, —OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴,—S(O)₂R²⁴, —S(O)NR²⁴R^(24′), —S(O)₂NR²⁴R^(24′), —OS(O)NR²⁴R^(24′),—OS(O)₂NR²⁴R^(24′), —NR²⁴R^(24′), —NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵,—NR²⁴C(O)NR²⁵R^(25′), —NR²⁴S(O)R²⁵, —NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^(25′),—NR²⁴S(O)₂NR²⁵R^(25′), —C(O)R²⁴, —C(O)OR²⁴ or —C(O)NR²⁴R^(24′);

R¹⁸ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR²⁶,—OC(O)R²⁶, —OC(O)NR²⁶R^(26′), —OS(O)R²⁶, —OS(O)₂R²⁶, —SR²⁶, —S(O)R²⁶,—S(O)₂R²⁶, —S(O)NR²⁶R^(26′), —S(O)₂NR²⁶R^(26′), —OS(O)NR²⁶R^(26′),—OS(O)₂NR²⁶R^(26′), —NR²⁶R^(26′), —NR²⁶C(O)R²⁷, —NR²⁶C(O)OR²⁷,—NR²⁶C(O)NR²⁷R^(27′), —NR²⁶C(═NR^(26′))NR²⁷R^(27′), —NR²⁶S(O)R²⁷,—NR²⁶S(O)₂R²⁷, —NR²⁶S(O)NR²⁷R^(27′), —NR²⁶S(O)₂NR²⁷R^(27′), —C(O)R²⁶,—C(O)OR²⁶ and —C(O)NR²⁶R^(26′), wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, —(CH₂)_(p)OR²⁸, —(CH₂)_(p)(OCH₂)_(q)OR²⁸,—(CH₂)_(p)(OCH₂CH₂)_(q)OR²⁸, —OR²⁹, —OC(O)R²⁹, —OC(O)NR²⁹R^(29′),—OS(O)R²⁹, —OS(O)₂R²⁹, —(CH₂)_(p)OS(O)₂₀R²⁹, —OS(O)₂OR²⁹, —SR²⁹,—S(O)R²⁹, —S(O)₂R²⁹, —S(O)NR²⁹R^(29′), —S(O)₂NR²⁹R^(29′),—OS(O)NR²⁹R^(29′), —OS(O)₂NR²⁹R^(29′), —NR²⁹R^(29′), —NR²⁹C(O)R³⁰,—NR²⁹C(O)OR³⁰, —NR²⁹C(O)NR³⁰R^(30′), —NR²⁹S(O)R³⁰, —NR²⁹S(O)₂R³⁰,—NR²⁹S(O)NR³⁰R^(30′), —NR²⁹S(O)₂NR³⁰R^(30′), —C(O)R²⁹, —C(O)OR²⁹ or—C(O)NR²⁹R^(29′);

each R¹⁹, R^(19′), R²⁰, R^(20′), R²¹, R^(21′), R²², R^(22′), R²³,R^(23′), R²⁴, R^(24′), R²⁵, R^(25′), R²⁶, R^(26′), R^(26″), R²⁹,R^(29′), R³⁰ and R^(30′) is independently selected from the groupconsisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl, wherein each hydrogen atom in C₁-C₇ alkyl, C₂-C₇alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, or 5- to 7-membered heteroaryl isindependently optionally substituted by halogen, —OH, —SH, —NH₂ or—CO₂H;

R²⁷ and R^(27′) are each independently selected from the groupconsisting of H, C₁-C₉ alkyl, C₂-C₉ alkenyl, C₂-C₉ alkynyl, C₃-C₆cycloalkyl, —(CH₂)_(p)(sugar), —(CH₂)_(p)(OCH₂CH₂)_(q)-(sugar) and—(CH₂)_(p)(OCH₂CH₂CH₂)_(q)(sugar);

R²⁸ is a H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5;

L² is a releasable linker;

L³ is selected from the group consisting of C₁-C₆ alkyl,—(CR³⁹R^(39′))_(r)C(O)—, —(CR³⁹R^(39′))_(r)OC(O)—,—NR³⁹R^(39′)C(O)(CR³⁹R^(39′))_(r)—, —(CH₂)_(r)NR³⁹—,—(OCR³⁹R^(39′)CR³⁹R^(39′))_(r)C(O)—, and—(OCR³⁹R^(39′)CR³⁹R^(39′)CR³⁹R^(39′))—_(r)C(O)—,

wherein

each R³⁹ and R^(39′) is independently selected from the group consistingof H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR⁴⁰, —OC(O)R⁴⁰, —OC(O)NR⁴⁰R^(40′), —OS(O)R⁴⁰,—OS(O)₂R⁴⁰, —SR⁴⁰, —S(O)R⁴⁰, —S(O)₂R⁴⁰, —S(O)NR⁴⁰R^(40′),—S(O)₂NR⁴⁰R^(40′), —OS(O)NR⁴⁰R^(40′), —OS(O)₂NR⁴⁰R^(40′), —NR⁴⁰R^(40′),—NR⁴⁰C(O)R⁴¹, —NR⁴⁰C(O)OR⁴¹, —NR⁴⁰C(O)NR⁴¹R^(41′), —NR⁴⁰S(O)R⁴¹,—NR⁴⁰S(O)₂R⁴¹, —NR⁴⁰S(O)NR⁴¹R^(41′), —NR⁴⁰S(O)₂NR⁴¹R^(41′), —C(O)R⁴⁰,—C(O)OR⁴⁰ and —C(O)NR⁴⁰R^(40′);

R⁴⁰, R^(40′), R⁴¹ and R^(41′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

r in each instance is 1, 2, 3, 4, or 5;

L⁴ is selected from the group consisting of —C(O)(CR⁴⁴R^(44′))_(t)—,—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(OCR⁴⁴R^(44′)CR⁴⁴R^(44′))_(t)—,—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(OCR⁴⁴R^(44′)CR⁴⁴R^(44′))_(t)—,—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(OCR⁴⁴R^(44′) CR⁴⁴R^(44′))_(t)C(O)—,—NR⁴²CR⁴³R⁴³R^(43′)CR⁴³R^(43′)(CR⁴⁴═CR^(44′))_(t)—, and —NR⁴²C₆-C₁₀aryl(C₁-C₆ alkyl)OC(O)—;

wherein

R⁴² is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR⁴⁵,—OC(O)R⁴⁵, —OC(O)NR⁴⁵R^(45′), —OS(O)R⁴⁵, —OS(O)₂R⁴⁵, —SR⁴⁵, —S(O)R⁴⁵,—S(O)₂R⁴⁵, —S(O)NR⁴⁵R^(45′), —S(O)₂NR⁴⁵R^(45′), —OS(O)NR⁴⁵R^(45′),—OS(O)₂NR⁴⁵R^(45′), —NR⁴⁵R^(45′), —NR⁴⁵C(O)R⁴⁶, —NR⁴⁵C(O)OR⁴⁶,—NR⁴⁵C(O)NR⁴⁶R^(46′), —NR⁴⁵S(O)R⁴⁶, —NR⁴⁵S(O)₂R⁴⁶, —NR⁴⁵S(O)NR⁴⁶R^(46′),—NR⁴⁵S(O)₂NR⁴⁶R^(46′), —C(O)R⁴⁵, —C(O)OR⁴⁵ or —C(O)NR⁴⁵R^(45′),

each R⁴³, R^(43′), R⁴⁴ and R⁴⁴ is independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl and C₃-C₆ cycloalkyl is independently optionallysubstituted by halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR⁴⁷, —OC(O)R⁴⁷, —OC(O)NR⁴⁷R^(47′), —OS(O)R⁴⁷,—OS(O)₂R⁴⁷, —SR⁴⁷, —S(O)R⁴⁷, —S(O)₂R⁴⁷, —S(O)NR⁴⁷R^(47′),—S(O)₂NR⁴⁷R^(47′), —OS(O)NR⁴⁷R^(47′), —OS(O)₂NR⁴⁷R^(47′), —NR⁴⁷R^(47′),—NR⁴⁷C(O)R⁴⁸, —NR⁴⁷C(O)OR⁴⁸, —NR⁴⁷C(O)NR⁴⁸R^(48′), —NR⁴⁷S(O)R⁴⁸,—NR⁴⁷S(O)₂R⁴⁸, —NR⁴⁷S(O)NR⁴⁸R^(48′), —NR⁴⁷S(O)₂NR⁴⁸R^(48′), —C(O)R⁴⁷,—C(O)OR⁴⁷ or —C(O)NR⁴⁷R^(47′);

R⁴⁵, R^(45′), R⁴⁶, R^(46′), R⁴⁷, R^(47′), R⁴⁸ and R^(48′) are eachindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl;

t is in each instance 1, 2, 3, 4, or 5;

L⁵ is selected from the groups consisting of C₁-C₁₀ alkyl,—(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— and—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)—, wherein

each R⁴⁹ and R^(49′) is independently selected from the group consistingof H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl,wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyland C₃-C₆ cycloalkyl is independently optionally substituted by halogen,C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl,—OR⁵⁰, —OC(O)R⁵⁰, —OC(O)NR⁵⁰R^(50′), —OS(O)R⁵⁰, —OS(O)₂R⁵⁰, —SR⁵⁰,—S(O)R⁵⁰, —S(O)₂R⁵⁰, —S(O)NR⁵⁰R^(50′), —S(O)₂NR⁵⁰R^(50′),—OS(O)NR⁵⁰R^(50′), —OS(O)₂NR⁵⁰R^(50′), —NR⁵⁰R^(50′), —NR⁵⁰C(O)R⁵¹,—NR⁵⁰C(O)OR⁵¹, —NR⁵⁰C(O)NR⁵¹R^(51′), —NR⁵⁰S(O)R⁵¹, —NR⁵⁰S(O)₂R⁵¹,—NR⁵⁰S(O)NR⁵¹R^(51′), —NR⁵⁰S(O)₂NR⁵¹R^(51′), —C(O)R⁵⁰, —C(O)OR⁵⁰ or—C(O)NR⁵⁰R^(50′);

R⁵⁰, R^(50′), R⁵¹ and R^(51′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl;

u is in each instance 0, 1, 2, 3, 4 or 5;

D¹ is a PBD prodrug; and

D² is a DNA binding agent;

or a pharmaceutically acceptable salt thereof.2. The conjugate of clause 1, wherein D¹ is of the formula III

wherein

R^(1a), R^(2a), R^(3a) and R^(4a) are each independently selected fromthe group consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(11a), —C(O)OR^(11a), and—C(O)NR^(11a)R^(11a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(11a), —OC(O)R^(11a),—OC(O)NR^(11a)R^(11a′), —OS(O)R^(11a), —OS(O)₂R^(11a), —SR^(11a),—S(O)R^(11a), —S(O)₂R^(11a), —S(O)NR^(11a)R^(11a′),—S(O)₂NR^(11a)R^(11a′), —OS(O)NR^(11a)R^(11a′), —OS(O)₂NR^(11a)R^(11a′),—NR^(11a)R^(11a′), —NR^(11a)C(O)R^(12a), —NR^(11a)C(O)OR^(12a),—NR^(11a)C(O)NR^(12a)R^(12a′), —NR^(11a)S(O)R^(12a),—NR^(11a)S(O)₂R^(12a), —NR^(11a)S(O)NR^(12a)R^(12a′),—NR^(11a)S(O)₂NR^(12a)R^(12a′), —C(O)R^(11a), —C(O)OR^(11a) or—C(O)NR^(11a)R^(11a′); or R^(11a) is a bond; or R^(4a) is a bond;

R^(5a), R^(6a) and R^(7a) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(13a), —C(O)OR^(13a) and—C(O)NR^(13a)R^(13a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isoptionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR^(14a), —OC(O)R^(14a), —OC(O)NR^(14a)R^(14a′),—OS(O)R^(14a), —OS(O)₂R^(14a), —SR^(14a), —S(O)R^(14a), —S(O)₂R^(14a),—S(O)NR^(14a)R^(14a′), —S(O)₂NR^(14a)R^(14a′), —OS(O)NR^(14a)R^(14a′),—OS(O)₂NR^(14a)R^(14a′), —NR^(14a)R^(14a′), —NR^(14a)C(O)R^(15a),—NR^(14a)C(O)OR^(15a), —NR^(14a)C(O)NR^(15a)R^(15a′),—NR^(14a)S(O)R^(15a), —NR^(14a)S(O)₂R^(15a),—NR^(14a)S(O)NR^(15a)R^(15a′), —NR^(14a)S(O)₂NR^(15a)R^(15a′),—C(O)R^(14a), —C(O)OR^(14a) or —C(O)NR^(14a)R^(14a′); wherein R^(6a) andR^(7a) taken together with the atoms to which they are attachedoptionally combine to form a 3- to 7-membered heterocycloalkyl, orR^(5a) and R^(6a) taken together with the atoms to which they areattached optionally combine to form a 3- to 7-membered heterocycloalkylor 5- to 7-membered heteroaryl, wherein each hydrogen atom in 3- to7-membered heterocycloalkyl or 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(16a), —OC(O)R^(16a),—OC(O)NR^(16a)R^(16a′), —OS(O)R^(16a), —OS(O)₂R^(16a), —SR^(16a),—S(O)R^(16a), —S(O)₂R^(16a), —S(O)NR^(16a)R^(16a′),—S(O)₂NR^(16a)R^(16a′), —OS(O)NR^(16a)R^(16a′), —OS(O)₂NR^(16a)R^(16a′),—NR^(16a)R^(16a′), —NR^(16a)C(O)R^(17a), —NR^(16a)C(O)CH₂CH₂ ⁻,—NR^(16a)C(O)OR^(17a), —NR^(16a)C(O)NR^(17a)R^(17a′),—NR^(16a)S(O)R^(17a), —NR^(16a)S(O)₂R^(17a),—NR^(16a)S(O)NR^(17a)R^(17a′), —NR^(16a)S(O)₂NR^(17a)R^(17a′),—C(O)R^(16a), —C(O)OR^(16a) or —C(O)NR^(16a)R^(16a′), and wherein onehydrogen atom in 5- to 7-membered heteroaryl is optionally a bond, orR^(5a) is a bond;

R^(8a) and R^(9a) are each independently selected from the groupconsisting of H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OR^(18a), —OC(O)R^(18a),—OC(O)NR^(18a)R^(18a′), —OS(O)R^(18a), —OS(O)₂R^(18a), —SR^(18a),—S(O)R^(18a), —S(O)₂R^(18a), —S(O)NR^(18a)R^(18a′),—S(O)₂NR^(18a)R^(18a′), —OS(O)NR^(18a)R^(18a′), —OS(O)₂NR^(18a)R^(18a′),—NR^(18a)R^(18a′), —NR^(18a)C(O)R^(19a), —NR^(18a)C(O)OR^(19a),—NR^(18a)C(O)NR^(19a)R^(19a′), —NR^(18a)S(O)R^(19a),—NR^(18a)S(O)₂R^(19a), —NR^(18a)S(O)NR^(19a)R^(19a′),—NR^(18a)S(O)₂NR^(19a)R^(19a′), —C(O)R^(18a), —C(O)OR^(18a) and—C(O)NR^(18a)R^(18a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(20a), —OC(O)R^(20a),—OC(O)NR^(20a)R^(20a′), —OS(O)R^(20a), —OS(O)₂R^(20a), —SR^(20a),—S(O)R^(20a), —S(O)₂R^(20a), —S(O)NR^(20a)R^(20a′),—S(O)₂NR^(20a)R^(20a′), —OS(O)NR^(20a)R^(20a′), —OS(O)₂NR^(20a)R^(20a′),—NR^(20a)R^(20a′), —NR^(20a)C(O)R^(21a), —NR^(20a)C(O)OR^(21a),—NR^(20a)C(O)NR^(21a)R^(21a′), —NR^(20a)S(O)R^(21a),—NR^(20a)S(O)₂R^(21a), —NR^(20a)S(O)NR^(21a)R^(21a′),—NR^(20a)S(O)₂NR^(21a)R^(21a′), —C(O)R^(20a), —C(O)OR^(20a) or—C(O)NR^(20a)R^(20a′);

R^(10a) is selected from the group consisting of H, D, C₁-C₆ alkyl,C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(22a),—OC(O)R^(22a), —OC(O)NR^(22a)R^(22a′), —OS(O)R^(22a), —OS(O)₂R^(22a),—SR^(22a), —S(O)R^(22a), —S(O)₂R^(22a), —S(O)NR^(22a)R^(22a′),—S(O)₂NR^(22a)R^(22a′), —OS(O)NR^(22a)R^(22a′), —OS(O)₂NR^(22a)R^(22a′),—NR^(22a)R^(22a′), —NR^(22a)C(O)R^(23a), —NR^(22a)C(O)OR^(23a),—NR^(22a)C(O)NR^(23a)R^(23a)R^(23a′), —NR^(22a)S(O)R^(23a),—NR^(22a)S(O)₂R^(23a), —NR^(22a)S(O)NR^(23a)R^(23a′),—NR^(22a)S(O)₂NR^(23a)R^(23a), —C(O)R^(22a), —C(O)OR^(23a) and—C(O)NR^(22a)R^(22a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(24a), —OC(O)R^(24a),—OC(O)NR^(24a)R^(24a′), —OS(O)R^(24a), —OS(O)₂R^(24a), —SR^(24a),—S(O)R^(24a), —S(O)₂R^(24a), —S(O)NR^(24a)R^(24a′),—S(O)₂NR^(24a)R^(24a′), —OS(O)NR^(24a)R^(24a′), —OS(O)₂NR^(24a)R^(24a′),—NR^(24a)R^(24a′), —NR^(24a)C(O)R^(25a), —NR^(24a)C(O)OR^(25a),—NR^(24a)C(O)NR^(25a)R^(25a′), —NR^(24a)S(O)R^(25a),—NR^(24a)S(O)₂R^(25a), —NR^(24a)S(O)NR^(25a)R^(25a′),—NR^(24a)S(O)₂NR^(25a)R^(25a′), —C(O)R^(24a), —C(O)OR^(24a) or—C(O)NR^(24a)R^(24a′); and

each R^(11a), R^(11a′), R^(12a), R^(12a′), R^(13a), R^(13a′), R^(14a),R^(14a′), R^(15a), R^(15a′), R^(16a), R^(16a′), R^(17a), R^(17a′),R^(18a), R^(18a′), R^(19a), R^(19a′), R^(20a), R^(20a′), R^(21a),R^(21a′), R^(22a), R^(22a′), R^(23a), R^(23a′), R^(24a), R^(24a′),R^(25a) and R^(25a′) is independently selected from the group consistingof H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₁₃ cycloalkyl,3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5- to 7-memberedheteroaryl;

provided that at least two of R^(1a), R^(4a) and R^(5a) are a bond, orwhen R^(5a) and R^(6a) taken together with the atoms to which they areattached optionally combine to form a 3- to 7-membered heterocycloalkylor 5- to 7-membered heteroaryl, one hydrogen atom in 5- to 7-memberedheteroaryl is a bond and one of R^(1a) or R^(4a) is a bond; or apharmaceutically acceptable salt thereof.

3. The conjugate of clause 1 or 2, wherein D² is a minor groove bindingdrug; or a pharmaceutically acceptable salt thereof.4. The conjugate of any one of clauses 1 to 3, wherein D² is of theformula selected from the group consisting of

wherein

R^(1b), R^(2b), R^(3b) and R^(4b) are each independently selected fromthe group consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(13b), —C(O)OR^(13b), and—C(O)NR^(13b)R^(13b′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(13b), —OC(O)R^(13b),—OC(O)NR^(13b)R^(13b′), —OS(O)R^(13b), —OS(O)₂R^(13b), —SR^(13b),—S(O)R^(13b), —S(O)₂R^(13b), —S(O)NR^(13b)R^(13b′),—S(O)₂NR^(13b)R^(13b′), —OS(O)NR^(13b)R^(13b′), —OS(O)₂NR^(13b)R^(13b′),—NR^(13b)R^(13b′), —NR^(13b)C(O)R^(14b), —NR^(13b)C(O)OR^(14b),—NR^(13b)C(O)NR^(14b)R^(14b′), —NR^(13b)S(O)R^(14b),—NR^(13b)S(O)₂R^(14b), —NR^(13b)S(O)NR^(14b)R^(14b′),—NR^(13b)S(O)₂NR^(14b)R^(14b′), —C(O)R^(13b), —C(O)OR^(13b) or—C(O)NR^(13b)R^(13b′); or any one of R^(1b), R^(2b), R^(3b) and R^(4b)is a bond;

R^(5b), R^(6b) and R^(7b) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(15b), —C(O)OR^(15b), and—C(O)NR^(15b)R^(15b′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, -L⁴H, -L³H, —OR^(15b),—OC(O)R^(15b), —OC(O)NR^(15b)R^(15b′), —OS(O)R^(15b), —OS(O)₂R^(15b),—SR^(15b), —S(O)R^(15b), —S(O)₂R^(15b), —S(O)NR^(15b)R^(15b′),—S(O)₂NR^(15b)R^(15b′), —OS(O)NR^(15b)R^(15b′), —OS(O)₂NR^(15b)R^(15b′),—NR^(15b)R^(15b′), —NR^(15b)C(O)R^(16b), —NR^(15b)C(O)OR^(16b),—NR^(15b)C(O)NR^(16b)R^(16b′), —NR^(15b)S(O)R^(16b),—NR^(15b)S(O)₂R^(16b), —NR^(15b)S(O)NR^(16b)R^(16b′),—NR^(15b)S(O)₂NR^(16b)R^(16b′), —C(O)R^(15b), —C(O)OR^(15b) or—C(O)NR^(15b)R^(15b′); wherein R^(6b) and R^(7b) taken together with theatoms to which they are attached optionally combine to form a 3- to7-membered heterocycloalkyl, or R^(5b) and R^(6b) taken together withthe atoms to which they are attached optionally combine to form a 3- to7-membered heterocycloalkyl or 5- to 7-membered heteroaryl, wherein eachhydrogen atom in 3- to 7-membered heterocycloalkyl and 5- to 7-memberedheteroaryl is independently optionally substituted by C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(17b),—OC(O)R^(17b), —OC(O)NR^(17b)R^(17b′), —OS(O)R^(17b), —OS(O)₂R¹⁷,—SR^(17b), —S(O)R^(17b), —S(O)₂R^(17b), —S(O)NR^(17b)R^(17b′),—S(O)₂NR^(17b)R^(17b′), —OS(O)NR^(17b)R^(17b′), —OS(O)₂NR^(17b)R^(17b′),—NR^(17b)R^(17b′), —NR^(17b)C(O)R^(18b), —NR^(17b)C(O)OR^(18b),—NR^(17b)C(O)NR^(18b)R^(18b′), —NR^(17b)S(O)R^(18b),—NR^(17b)S(O)₂R^(18b), —NR^(17b)S(O)NR^(18b)R^(18b′),—NR^(17b)S(O)₂NR^(18b)R^(18b′), —C(O)R^(17b), —C(O)OR^(17b) or—C(O)NR^(17b)R^(17b); or any one of R^(5b), R^(6b) or R^(7b) is a bond;

R^(8b) and R^(9b) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OR^(19b), —OC(O)R^(19b),—OC(O)NR^(19b)R^(19b′), —OS(O)R^(19b), —OS(O)₂R^(19b), —SR^(19b),—S(O)R^(19b), —S(O)₂R^(19b), —S(O)NR^(19b)R^(19b′),—S(O)₂NR^(19b)R^(19b′), —OS(O)NR^(19b)R^(19b′), —OS(O)₂NR^(19b)R^(19b′),—NR^(19b)R^(19b′), —NR^(19b)C(O)R^(20b), —NR^(19b)C(O)OR^(20b),—NR^(19b)C(O)NR^(20b)R^(20b′), —NR^(19b)S(O)R^(20b),—NR^(19b)S(O)₂R^(20b), —NR^(19b)S(O)NR^(2b)R^(20b′),—NR^(19b)S(O)₂NR^(20b)R^(20b′), —C(O)R^(19b), —C(O)OR^(19b) and—C(O)NR^(19b)R^(19b′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(21b), —OC(O)R^(21b),—OC(O)NR^(21b)R^(21b′), —OS(O)R^(21b), —OS(O)₂R^(21b), —SR^(21b),—S(O)R^(21b), —S(O)₂R^(2b), —S(O)NR^(21b)R^(21b′),—S(O)₂NR^(21b)R^(21b′), —OS(O)NR^(21b)R^(21b′), —OS(O)₂NR^(21b)R^(21b′),—NR^(21b)R^(21b′), —NR^(21b)C(O)R^(22b), —NR^(21b)C(O)OR^(22b),—NR^(21b)C(O)NR^(22b)R^(22b′), —NR^(21b)S(O)R^(22b),—NR^(21b)S(O)₂R^(22b), —NR^(21b)S(O)NR^(22b)R^(22b′),—NR^(21b)S(O)₂NR^(22b)R^(22b′), —C(O)R^(21b), —C(O)OR^(21b) or—C(O)NR^(21b)R^(21b);

R^(10b), R^(11b) and R^(12b) are each independently selected from thegroup consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR^(23b), —OC(O)R^(23b), —OC(O)NR^(23b)R^(23b′),—OS(O)R^(23b), —OS(O)₂R^(23b), —SR^(23b), —S(O)R^(23b), —S(O)₂R^(23b),—S(O)NR^(23b)R^(23b′), —S(O)₂NR^(23b)R^(23b′), —OS(O)NR^(23b)R^(23b′),—OS(O)₂NR^(23b)R^(23b′), —NR^(23b)R^(23b′), —NR^(23b)C(O)R^(24b),—NR^(23b)C(O)OR^(24b), —NR^(23b)C(O)NR^(24b)R^(24b′),—NR^(23b)S(O)R^(24b), —NR^(23b)S(O)₂R^(24b),—NR^(23b)S(O)NR^(24b)R^(24b′), —NR^(23b)S(O)₂NR^(24b)R^(24b′),—C(O)R^(23b), —C(O)OR^(23b) and —C(O)NR^(23b)R^(23b′), wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl is independently optionally substituted by C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(25b),—OC(O)R^(25b), —OC(O)NR^(25b)R^(25b′), —OS(O)R^(25b), —OS(O)₂R^(25b),—SR^(25b), —S(O)R^(25b), —S(O)₂R^(25b), —S(O)NR^(25b)R^(25b′),—S(O)₂NR^(25b)R^(25b′), —OS(O)NR^(25b)R^(25b′), —OS(O)₂NR^(25b)R^(25b′),—NR^(25b)R^(25b′), —NR^(25b)C(O)R^(26b), —NR^(25b)C(O)OR^(26b),—NR^(25b)C(O)NR^(26b)R^(26b′), —NR^(25b)S(O)R^(26b),—NR^(25b)S(O)₂R^(26b), —NR^(25b)S(O)NR^(26b)R^(26b′),—NR^(25b)S(O)₂NR^(26b)R^(26b′), —C(O)R^(25b), —C(O)OR^(25b) or—C(O)NR^(25b)R^(25b), or R^(10b) and R^(11b) taken together with thecarbon atoms to which they are attached optionally combine to form aC₆-C₁₀ aryl, or R^(11b) and R^(12b) taken together with the carbon atomto which they are attached optionally combine to form an exo-methylene;or R^(12b) is absent;

each R^(13b), R^(13b′), R^(14b), R^(14b′), R^(15b), R^(15b′), R^(16b),R^(16b′), R^(17b), R^(17b′), R^(18b), R^(18b′), R^(19b), R^(19b′),R^(20b), R^(20b′), R^(21b), R^(21b′), R^(22b), R^(22b′), R^(23b),R^(23b′), R^(24b), R^(24b′), R^(25b), R^(25b′), R^(26b) and R^(26b′) isindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₁₃ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, C₁-C₆ alkyl(C₆-C₁₀ aryl) and 5- to7-membered heteroaryl, wherein each hydrogen atom in C₆-C₁₀ aryl, C₁-C₆alkyl(C₆-C₁₀ aryl) and 5- to 7-membered heteroaryl is independentlyoptionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OH, —SH, —NH₂, —SO₃H, —C(O)OHand —C(O)NH₂;

provided that one of R^(1b), R^(2b), R^(3b), R^(4b), R^(5b), R^(6b) andR^(7b) is a bond;

R^(1c), R^(2c) and R^(5c) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(6c), —C(O)OR^(6c) and—C(O)NR^(6c)R^(6c′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(7c), —OC(O)R^(7c),—OC(O)NR^(7c)R^(7c′), —OS(O)R^(7c), —OS(O)₂R^(7c), —SR^(7c),—S(O)R^(7c), —S(O)₂R^(7c), —S(O)₂OR^(7c), —S(O)NR^(7c)R^(7c′),—S(O)₂NR^(7c)R^(7c′), —OS(O)NR^(7c)R^(7c′), —OS(O)₂NR^(7c)R^(7c′),—NR^(7c)R^(7c′), —NR^(7c)C(O)R^(8c), —NR^(7c)C(O)OR^(8c),—NR^(7c)C(O)NR^(8c)R^(8c′), —NR^(7c)S(O)R^(8c), —NR^(7c)S(O)₂R^(8c),—NR^(7c)S(O)NR^(8c)R^(8c′), —NR^(7c)S(O)₂NR^(8c)R^(8c′), —C(O)R^(7c),—C(O)OR^(7c) or —C(O)NR^(7c)R^(7c′); or when J is —CR^(13c)═, R^(5c) isabsent; provided that one of R^(1c) or R^(2c) is a bond;

R^(3c) and R^(4c) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OR^(9c), —OC(O)R^(9c),—OC(O)NR^(9c)R^(9c′), —OS(O)R^(9c), —OS(O)₂R^(9c), —SR^(9c),—S(O)R^(9c), —S(O)₂R^(9c), —S(O)NR^(9c)R^(9c′), —S(O)₂NR^(9c)R^(9c′),—OS(O)NR^(9c)R^(9c′), —OS(O)₂NR^(9c)R^(9c′), —NR^(9c)R^(9c′),—NR^(9c)C(O)R^(10c), —NR^(9c)C(O)OR^(10c), —NR^(9c)C(O)NR^(10c)R^(10c′),—NR^(9c)S(O)R^(10c), —NR^(9c)S(O)₂R^(10c), —NR^(9c)S(O)NR^(10c)R^(10c′),—NR^(9c)S(O)₂NR^(10c)R^(10c′), —C(O)R^(9c), —C(O)OR^(9c) and—C(O)NR^(9c)R^(9c′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(11c), —OC(O)R^(11c),—OC(O)NR^(11c)R^(11c′), —OS(O)R^(11c), —OS(O)₂R^(11c), —SR^(11c),—S(O)R^(11c), —S(O)₂R^(11c), —S(O)NR^(11c)R^(11c′),—S(O)₂NR^(11c)R^(11c′), —OS(O)NR^(11c)R^(11c′), —OS(O)₂NR^(11c)R^(11c′),—NR^(11c)R^(11c′), —NR^(11c)C(O)R^(12c), —NR^(11c)C(O)OR^(12c),—NR^(11c)C(O)NR^(12c)R^(12c′), —NR^(11c)S(O)R^(12c),—NR^(11c)S(O)₂R^(12c), —NR^(11c)S(O)NR^(12c)R^(12c′),—NR^(11c)S(O)₂NR^(12c)R^(12c′), —C(O)R^(11c), —C(O)OR^(11c) or—C(O)NR^(11c)R^(11c);

J is —C(O)—, —CR^(13c)═ or —(CR^(13c)R^(13c′))—

each R^(6c), R^(6c′), R^(7c), R^(7c′), R^(8c), R^(8c′), R^(9c), R^(9c′),R^(10c), R^(10c′), R^(11c), R^(11c′), R^(12c), R^(12c′), R^(13c) andR^(13c′) is independently selected from the group consisting of H, D,C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-memberedheteroaryl;

R^(1d) is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(2d),—SR^(2d) and —NR^(2d)R^(2d′),

R^(2d) and R^(2d′) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl, wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isoptionally substituted by —OR^(3d), —SR^(3d), and —NR^(3d)R^(3d′);

R^(3d) and R^(3d′) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl;

R^(1e) is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl, whereineach hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl is independently optionally substituted by C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(2e),—OC(O)R^(2e), —OC(O)NR^(2e)R^(2e′), —OS(O)R^(2e), —OS(O)₂R^(2e),—SR^(2e), —S(O)R^(2e), —S(O)₂R^(2e), —S(O)NR^(2e)R^(2e′),—S(O)₂NR^(2e)R^(2e′), —OS(O)NR^(2e)R^(2e′), —OS(O)₂NR^(2e)R^(2e′),—NR^(2e)R^(2e′), —NR^(2e)C(O)R^(3e), —NR^(2e)C(O)OR^(3e),—NR^(2e)C(O)NR^(3e)R^(3e′), —NR^(2e)S(O)R^(3e), —NR^(2e)S(O)₂R^(3e),—NR^(2e)S(O)NR^(2e)R^(2e′), —NR^(2e)S(O)₂NR^(3e)R^(3e′), —C(O)R^(2e),—C(O)OR^(2e) or —C(O)NR^(2e)R^(2e);

each R^(2e), R^(2e′), R^(3e) and R^(3e′) is independently selected fromthe group consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl, wherein each hydrogen atom in C₁-C₆ alkyl,C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isoptionally substituted by —OR^(4e), —SR^(4e) or —NR^(4e)R^(4e′);

R^(4e) and R^(4e′) are independently selected from the group consistingof H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3-to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-memberedheteroaryl;

v is 1, 2 or 3; and

* is a covalent bond;

or a pharmaceutically acceptable salt thereof.5. The conjugate of any one of clauses 1 to 4, wherein each AA isindependently selected from the group consisting of L-lysine,L-asparagine, L-threonine, L-serine, L-isoleucine, L-methionine,L-proline, L-histidine, L-glutamine, L-arginine, L-glycine, L-asparticacid, L-glutamic acid, L-alanine, L-valine, L-phenylalanine, L-leucine,L-tyrosine, L-cysteine, L-tryptophan, L-phosphoserine, L-sulfo-cysteine,L-arginosuccinic acid, L-hydroxyproline, L-phosphoethanolamine,L-sarcosine, L-taurine, L-carnosine, L-citrulline, L-anserine,L-1,3-methyl-histidine, L-alpha-amino-adipic acid, D-lysine,D-asparagine, D-threonine, D-serine, D-isoleucine, D-methionine,D-proline, D-histidine, D-glutamine, D-arginine, D-glycine, D-asparticacid, D-glutamic acid, D-alanine, D-valine, D-phenylalanine, D-leucine,D-tyrosine, D-cysteine, D-tryptophan, D-citrulline and D-carnosine, or apharmaceutically acceptable salt thereof.6. The conjugate of any one of clauses 1 to 5, wherein R¹⁶ is H; or apharmaceutically acceptable salt thereof.7. The conjugate of any one of clauses 1 to 6, wherein each R¹⁷ andR^(17′) is independently selected from the group consisting of H, C₁-C₆alkyl and —OR²², wherein each hydrogen atom in C₁-C₆ alkyl isindependently optionally substituted by —OR²⁴; or R¹⁷ and R^(17′) maycombine to form a C₄-C₆ cycloalkyl or a 4- to 6-membered heterocycle,wherein each hydrogen atom in C₄-C₆ cycloalkyl or 4- to 6-memberedheterocycle is independently optionally substituted by halogen, C₁-C₆alkyl or —OR²⁴; or a pharmaceutically acceptable salt thereof.8. The conjugate of any one of clauses 1 to 7, wherein R¹⁸ is selectedfrom the group consisting of H, C₁-C₆ alkyl, 5- to 7-memberedheteroaryl, —OR²⁶, —NR²⁶C(O)R²⁷, —NR²⁶C(O)NR²⁷R^(27′),—NR²⁶C(═NR^(26′))NR²⁷R^(27′), and —C(O)NR²⁶R^(26′), wherein eachhydrogen atom in C₁-C₆ alkyl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, —OR²⁹,—(CH₂)_(p)OS(O)₂OR²⁹, —OS(O)₂OR²⁹, or —C(O)NR²⁹R^(29′);

each R²⁶, R^(26′), R^(26′), R²⁹ and R^(29′) is independently H or C₁-C₇alkyl, wherein each hydrogen atom in C₁-C₇ alkyl, is independentlyoptionally substituted by halogen, —OH, —SH, —NH₂ or —CO₂H;

R²⁷ and R^(27′) are each independently selected from the groupconsisting of H, C₁-C₉ alkyl, C₂-C₉ alkenyl, C₂-C₉ alkynyl, C₃-C₆cycloalkyl, —(CH₂)_(p)(sugar), —(CH₂)_(p)(OCH₂CH₂)_(q)-(sugar) and—(CH₂)_(p)(OCH₂CH₂CH₂)_(q)(sugar);

n is 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5;

or a pharmaceutically acceptable salt thereof.

9. The conjugate of any one of clauses 1 to 8, wherein each L¹ isselected from the group consisting of

wherein R¹⁶ is H, and * is a covalent bond; or a pharmaceuticallyacceptable salt thereof.10. The conjugate of any one of clauses 1 to 9, wherein R¹ and R² ineach instance are H; R³, R⁴, R⁵ and R⁶ are H; X¹ is —NR¹¹—; X² is ═N—;X³ is —N═; X⁴ is —N═; X⁵ is NR¹²; Y¹ is ═O; Y² is absent; R¹¹ and R¹²are H; m is 1, 2, 3 or 4; and * is a covalent bond; or apharmaceutically acceptable salt thereof.11. The conjugate of any one of clauses 1 to 10, having the formula

or a pharmaceutically acceptable salt thereof.12. The conjugate of any one of clauses 1 to 11, having the formula

or a pharmaceutically acceptable salt thereof.13. The conjugate of any one of clauses 1 to 12, wherein the sequence of-(AA)₄- is -Asp-Arg-Asp-Asp-; or a pharmaceutically acceptable saltthereof.14. The conjugate of any one of clauses 1 to 13, wherein the sequence of-(AA)₂- is Val-CIT; or a pharmaceutically acceptable salt thereof.15. The conjugate of any one of clauses 1 to 14, wherein L² is selectedfrom the group consisting of

wherein

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

X⁶ is C₁-C₆ alkyl or C₆-C₁₀ aryl(C₁-C₆ alkyl), wherein each hydrogenatom in C₁-C₆ alkyl and C₆-C₁₀ aryl(C₁-C₆ alkyl) is independentlyoptionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^(34′),—OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^(34′),—S(O)₂NR³⁴R^(34′), —OS(O)NR³⁴R^(34′), —OS(O)₂NR³⁴R^(34′), —NR³⁴R^(34′),—NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R³⁵, —NR³⁴S(O)R³⁵,—NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^(35′), —NR³⁴S(O)₂NR³⁵R^(35′), —C(O)R³⁴,—C(O)OR³⁴ or —C(O)NR³⁴R^(34′);

each R³², R^(32′), R³³, R^(33′), R³⁴, R^(34′), R³⁵ and R^(35′) areindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, and 5- to 7-membered heteroaryl;

R³⁶ is independently selected from the group consisting of H, D, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³⁷,—OC(O)R³⁷, —OC(O)NR³⁷R^(37′), —OS(O)R³⁷, —OS(O)₂R³⁷, —SR³⁷, —S(O)R³⁷,—S(O)₂R³⁷, —S(O)NR³⁷R^(37′), —S(O)₂NR³⁷R^(37′), —OS(O)NR³⁷R^(37′),—OS(O)₂NR³⁷R^(37′), —NR³⁷R^(37′), —NR³⁷C(O)R³⁸, —NR³⁷C(O)OR³⁸,—NR³⁷C(O)NR³⁸R^(38′), —NR³⁷S(O)R³⁸, —NR³⁷S(O)₂R³⁸, —NR³⁷S(O)NR³⁸R^(38′),—NR³⁷S(O)₂NR³⁸R^(38′), —C(O)R³⁷, —C(O)OR³⁷ or —C(O)NR³⁷R^(37′);

R³⁷, R^(37′), R³⁸ and R^(38′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl; and

* is a covalent bond;

or a pharmaceutically acceptable salt thereof.16. The conjugate of any one of clauses 1 to 15, wherein L² is of theformula

whereinR³¹ is H; and X⁶ is C₁-C₆ alkyl; or a pharmaceutically acceptable saltthereof.17. The conjugate of any one of clauses 1 to 15, wherein L² is of theformula

whereinR³¹ is H; and X⁶ is C₆-C₁₀ aryl(C₁-C₆ alkyl); or a pharmaceuticallyacceptable salt thereof.18. The conjugate of any one of clauses 1 to 15, wherein L² is of theformula

wherein

R³⁶ is independently selected from the group consisting of H, D, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³⁷,—OC(O)R³⁷, —OC(O)NR³⁷R^(37′), —OS(O)R³⁷, —OS(O)₂R³⁷, —SR³⁷, —S(O)R³⁷,—S(O)₂R³⁷, —S(O)NR³⁷R^(37′), —S(O)₂NR³⁷R^(37′), —OS(O)NR³⁷R^(37′),—OS(O)₂NR³⁷R^(37′), —NR³⁷R^(37′), —NR³⁷C(O)R³⁸, —NR³⁷C(O)OR³⁸,—NR³⁷C(O)NR³⁸R^(38′), —NR³⁷S(O)R³⁸, —NR³⁷S(O)₂R³⁸, —NR³⁷S(O)NR³⁸R^(38′),—NR³⁷S(O)₂NR³⁸R^(38′), —C(O)R³⁷, —C(O)OR³⁷ or —C(O)NR³⁷R^(37′);

R³⁷, R^(37′), R³⁸ and R^(38′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl; and

* is a covalent bond.

19. The conjugate of any one of clauses 1 to 15, wherein R³⁶ is H; or apharmaceutically acceptable salt thereof.20. The conjugate of any one of clauses 1 to 15, 18 or 19, wherein thelinker is of the formula

wherein * is a bond; or a pharmaceutically acceptable salt thereof.21. The conjugate of any one of clauses 1 to 15, 18 or 19, wherein thelinker is of the formula

wherein * is a bond; or a pharmaceutically acceptable salt thereof.22. The conjugate of any one of clauses 1 to 16, wherein the linker isof the formula

wherein * is a bond; or a pharmaceutically acceptable salt thereof.23. The conjugate of any one of clauses 1 to 16, wherein the linker isof the formula

wherein * is a bond; or a pharmaceutically acceptable salt thereof.24. The conjugate of any one of clauses 1 to 15 or 16, wherein thelinker is of the formula

wherein * is a bond; or a pharmaceutically acceptable salt thereof.25. The conjugate of any one of clauses 1 to 15, 18 or 19, wherein thelinker is of the formula

wherein * is a bond; or a pharmaceutically acceptable salt thereof.26. The conjugate of any one of clauses 1 to 15, 18 or 19, wherein thelinker is of the formula

wherein * is a bond; or a pharmaceutically acceptable salt thereof.27. The conjugate of any one of clauses 1 to 15, 18 or 19, wherein thelinker is of the formula

wherein * is a bond, or a pharmaceutically acceptable salt thereof.28. The conjugate of any one of clauses 1 to 15, 18 or 19, wherein thelinker is of the formula

wherein * is a bond, or a pharmaceutically acceptable salt thereof.29. The conjugate of any of clauses 1-28, wherein -D¹-L⁵-D² is of theformula

wherein R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a), R^(2b), R^(3b),R^(4b), R^(8b) and R^(9b) are H; or a pharmaceutically acceptable saltthereof.30. The conjugate of any of clause 29, wherein R^(2a), R^(3a), R^(4a),R^(8a), R^(9a), R^(10a), R^(2b), R^(3b), R^(4b), R^(8b) and R^(9b) areH, L⁵ is C₁-C₁₀ alkyl or —(CR⁴⁹R^(49′))_(u)C(O)—, each R⁴⁹ and R^(49′)is H, and u is 1, 2, 3, or 4; or a pharmaceutically acceptable saltthereof.31. The conjugate of any of clauses 1-28, wherein -D¹-L⁵-D² is of theformula

wherein R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a),R^(10a), R^(2c), R^(3c), R^(4c), R^(5c) are H; or a pharmaceuticallyacceptable salt thereof.32. The conjugate of any of clause 31, wherein, L⁵ is C₁-C₁₀ alkyl or—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 1,2, 3, 4 or 5; or a pharmaceutically acceptable salt thereof.33. The conjugate of any of clauses 1-28, wherein -D¹-L⁵-D² is of theformula

wherein, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a)and R^(10a) are H; or a pharmaceutically acceptable salt thereof.34. The conjugate of clause 33, wherein, L⁵ is C₁-C₁₀ alkyl or—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 1,2, 3, 4 or 5; or a pharmaceutically acceptable salt thereof.35. The conjugate of any of clauses 1-28, wherein -D¹-L⁵-D² is of theformula

wherein, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a),R^(10a) and R^(1e) are H; or a pharmaceutically acceptable salt thereof.36. The conjugate of clause 35, wherein L⁵ is C₁-C₁₀ alkyl or—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 1,2, 3, 4 or 5; or a pharmaceutically acceptable salt thereof.37. The conjugate of any of claims 1-28, wherein -D¹-L⁵-D² is of theformula

wherein R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a),R^(10a), R^(1d) are H; or a pharmaceutically acceptable salt thereof.38. The conjugate of clause 37, wherein L⁵ is C₁-C₁₀ alkyl or—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 1,2, 3, 4 or 5; or a pharmaceutically acceptable salt thereof.39. The conjugate of any of clauses 1-28, wherein -D¹-L⁵-D² is of theformula

wherein R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a)and R^(10a) are H; or a pharmaceutically acceptable salt thereof.40. The conjugate of clause 39, wherein L⁵ is C₁-C₁₀ alkyl or—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 1,2, 3, 4 or 5; or a pharmaceutically acceptable salt thereof.41. The conjugate of any of clauses 1-28, wherein -D¹-L⁵-D² is of theformula

wherein R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a)and R^(10a) are H; or a pharmaceutically acceptable salt thereof.42. The conjugate of clause 41, wherein L⁵ is C₁-C₁₀ alkyl or—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 1,2, 3, 4 or 5; or a pharmaceutically acceptable salt thereof.43. The conjugate of any of clauses 1-28, wherein -D¹-L⁵-D² is of theformula

wherein R^(2a), R^(3a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a), R^(10a),R^(2b), R^(3b), R^(4b), R^(5b), R^(6b), R^(7b), R^(8b), R^(9b), R^(10b),R^(11b) and R^(12b) are H; or a pharmaceutically acceptable saltthereof.44. The conjugate of clause 43, wherein L⁵ is C₁-C₁₀ alkyl or—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 1,2, 3, 4 or 5; or a pharmaceutically acceptable salt thereof.45. A conjugate of the formula

or a pharmaceutically acceptable salt thereof.46. A pharmaceutical composition comprising a therapeutically effectiveamount of a conjugate according to any one of clauses 1-45, or apharmaceutically acceptable salt thereof, and at least on excipient.47. A method of treating abnormal cell growth in a mammal, including ahuman, the method comprising administering to the mammal a conjugate ofany one of clauses 1-45.48. The method of clause 47, wherein the abnormal cell growth is cancer49. The method of clause 48, wherein the cancer is lung cancer, bonecancer, pancreatic cancer, skin cancer, cancer of the head or neck,cutaneous or intraocular melanoma, uterine cancer, ovarian cancer,rectal cancer, cancer of the anal region, stomach cancer, colon cancer,breast cancer, uterine cancer, carcinoma of the fallopian tubes,carcinoma of the endometrium, carcinoma of the cervix, carcinoma of thevagina, carcinoma of the vulva, Hodgkin's Disease, cancer of theesophagus, cancer of the small intestine, cancer of the endocrinesystem, cancer of the thyroid gland, cancer of the parathyroid gland,cancer of the adrenal gland, sarcoma of soft tissue, cancer of theurethra, cancer of the penis, prostate cancer, chronic or acuteleukemia, lymphocytic lymphomas, cancer of the bladder, cancer of thekidney or ureter, renal cell carcinoma, carcinoma of the renal pelvis,neoplasms of the central nervous system (CNS), primary CNS lymphoma,spinal axis tumors, brain stem glioma, pituitary adenoma, or acombination of one or more of the foregoing cancers. In anotherembodiment of said method, said abnormal cell growth is a benignproliferative disease, including, but not limited to, psoriasis, benignprostatic hypertrophy or restinosis.50. Use of a conjugate according to any one of clauses 1-45 in thepreparation of a medicament for the treatment of cancer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows that EC1629 (♦) dosed at 2 μmol/kg TIW for two weeksdecreases KB tumors in test animals compared to untreated control (●).The dotted line indicates the last dosing day.

FIG. 2 shows that EC1744 (▪) dosed at 2 μmol/kg TIW for two weeksdecreases KB tumors in test animals compared to untreated control (●).FIG. 2 also shows and that EC1788 (▴) dosed at 0.2 μmol/kg TIW for twoweeks decreases KB tumors in test animals compared to untreated control(●), and that EC1788 gave a complete response. The dotted line indicatesthe last dosing day.

FIG. 3 shows that EC1884 (d) dosed at 2 μmol/kg TIW for two weeksdecreases KB tumors in test animals compared to untreated control (a).FIG. 3 also shows and that EC1879 (c) dosed at 2 μmol/kg TIW for 1 weekdecreases KB tumors in test animals compared to untreated control (a),and that EC1879 gave a partial response. FIG. 3 also shows and thatEC1788 (b) dosed at 0.4 μmol/kg BIW for 2 weeks decreases KB tumors intest animals compared to untreated control (a), and that EC1788 gave acomplete response, and cure. The dotted line indicates the last dosingday.

FIG. 4 shows that EC1879 (▴) dosed at 2 μmol/kg TIW for two weeksdecreases KB tumors in test animals compared to untreated control (▪),and that EC1879 gave a complete response in 5/5 test animals, and curein 5/5 test animals. The dotted line indicates the last dosing day.

FIG. 5 shows that EC1744 (♦) dosed at 2 μmol/kg TIW for two weeksdecreases MDA-MB-231 tumors in test animals compared to untreatedcontrol (▪), and that EC1744 gave a complete response in 5/5 testanimals, and cure in 4/5 test animals. The dotted line indicates thelast dosing day.

DEFINITIONS

As used herein, the term “alkyl” includes a chain of carbon atoms, whichis optionally branched and contains from 1 to 20 carbon atoms. It is tobe further understood that in certain embodiments, alkyl may beadvantageously of limited length, including C₁-C₁₂, C₁-C₁₀, C₁-C₉,C₁-C₈, C₁-C₇, C₁-C₆, and C₁-C₄, Illustratively, such particularlylimited length alkyl groups, including C₁-C₈, C₁-C₇, C₁-C₆, and C₁-C₄,and the like may be referred to as “lower alkyl.” Illustrative alkylgroups include, but are not limited to, methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, 2-pentyl,3-pentyl, neopentyl, hexyl, heptyl, octyl, and the like. Alkyl may besubstituted or unsubstituted. Typical substituent groups includecycloalkyl, aryl, heteroaryl, heteroalicyclic, hydroxy, alkoxy, aryloxy,mercapto, alkylthio, arylthio, cyano, halo, carbonyl, oxo, (═O),thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl, N-thiocarbamyl,C-amido, N-amido, C-carboxy, O-carboxy, nitro, and amino, or asdescribed in the various embodiments provided herein. It will beunderstood that “alkyl” may be combined with other groups, such as thoseprovided above, to form a functionalized alkyl. By way of example, thecombination of an “alkyl” group, as described herein, with a “carboxy”group may be referred to as a “carboxyalkyl” group. Other non-limitingexamples include hydroxyalkyl, aminoalkyl, and the like.

As used herein, the term “alkenyl” includes a chain of carbon atoms,which is optionally branched, and contains from 2 to 20 carbon atoms,and also includes at least one carbon-carbon double bond (i.e. C═C). Itwill be understood that in certain embodiments, alkenyl may beadvantageously of limited length, including C₂-C₁₂, C₂-C₉, C₂-C₈, C₂-C₇,C₂-C₆, and C₂-C₄. Illustratively, such particularly limited lengthalkenyl groups, including C₂-C₈, C₂-C₇, C₂-C₆, and C₂-C₄ may be referredto as lower alkenyl. Alkenyl may be unsubstituted, or substituted asdescribed for alkyl or as described in the various embodiments providedherein. Illustrative alkenyl groups include, but are not limited to,ethenyl, 1-propenyl, 2-propenyl, 1-, 2-, or 3-butenyl, and the like.

As used herein, the term “alkynyl” includes a chain of carbon atoms,which is optionally branched, and contains from 2 to 20 carbon atoms,and also includes at least one carbon-carbon triple bond (i.e. C≡C). Itwill be understood that in certain embodiments alkynyl may each beadvantageously of limited length, including C₂-C₁₂, C₂-C₉, C₂-C₈, C₂-C₇,C₂-C₆, and C₂-C₄. Illustratively, such particularly limited lengthalkynyl groups, including C₂-C₈, C₂-C₇, C₂-C₆, and C₂-C₄ may be referredto as lower alkynyl. Alkenyl may be unsubstituted, or substituted asdescribed for alkyl or as described in the various embodiments providedherein. Illustrative alkenyl groups include, but are not limited to,ethynyl, 1-propynyl, 2-propynyl, 1-, 2-, or 3-butynyl, and the like.

As used herein, the term “aryl” refers to an all-carbon monocyclic orfused-ring polycyclic groups of 6 to 12 carbon atoms having a completelyconjugated pi-electron system. It will be understood that in certainembodiments, aryl may be advantageously of limited size such as C₆-C₁₀aryl. Illustrative aryl groups include, but are not limited to, phenyl,naphthalenyl and anthracenyl. The aryl group may be unsubstituted, orsubstituted as described for alkyl or as described in the variousembodiments provided herein.

As used herein, the term “cycloalkyl” refers to a 3 to 15 memberall-carbon monocyclic ring, an all-carbon 5-member/6-member or6-member/6-member fused bicyclic ring, or a multicyclic fused ring (a“fused” ring system means that each ring in the system shares anadjacent pair of carbon atoms with each other ring in the system) groupwhere one or more of the rings may contain one or more double bonds butthe cycloalkyl does not contain a completely conjugated pi-electronsystem. It will be understood that in certain embodiments, cycloalkylmay be advantageously of limited size such as C₃-C₁₃, C₃-C₆, C₃-C₆ andC₄-C₆. Cycloalkyl may be unsubstituted, or substituted as described foralkyl or as described in the various embodiments provided herein.Illustrative cycloalkyl groups include, but are not limited to,cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclopentadienyl,cyclohexyl, cyclohexenyl, cycloheptyl, adamantyl, norbornyl,norbornenyl, 9H-fluoren-9-yl, and the like.

As used herein, the term “heterocycloalkyl” refers to a monocyclic orfused ring group having in the ring(s) from 3 to 12 ring atoms, in whichat least one ring atom is a heteroatom, such as nitrogen, oxygen orsulfur, the remaining ring atoms being carbon atoms. Heterocycloalkylmay optionally contain 1, 2, 3 or 4 heteroatoms. Heterocycloalkyl mayalso have one of more double bonds, including double bonds to nitrogen(e.g. C═N or N═N) but does not contain a completely conjugatedpi-electron system. It will be understood that in certain embodiments,heterocycloalkyl may be advantageously of limited size such as 3- to7-membered heterocycloalkyl, 5- to 7-membered heterocycloalkyl, and thelike. Heterocycloalkyl may be unsubstituted, or substituted as describedfor alkyl or as described in the various embodiments provided herein.Illustrative heterocycloalkyl groups include, but are not limited to,oxiranyl, thianaryl, azetidinyl, oxetanyl, tetrahydrofuranyl,pyrrolidinyl, tetrahydropyranyl, piperidinyl, 1,4-dioxanyl, morpholinyl,1,4-dithianyl, piperazinyl, oxepanyl, 3,4-dihydro-2H-pyranyl,5,6-dihydro-2H-pyranyl, 2H-pyranyl, 1, 2, 3, 4-tetrahydropyridinyl, andthe like.

As used herein, the term “heteroaryl” refers to a monocyclic or fusedring group of 5 to 12 ring atoms containing one, two, three or four ringheteroatoms selected from nitrogen, oxygen and sulfur, the remainingring atoms being carbon atoms, and also having a completely conjugatedpi-electron system. It will be understood that in certain embodiments,heteroaryl may be advantageously of limited size such as 3- to7-membered heteroaryl, 5- to 7-membered heteroaryl, and the like.Heteroaryl may be unsubstituted, or substituted as described for alkylor as described in the various embodiments provided herein. Illustrativeheteroaryl groups include, but are not limited to, pyrrolyl, furanyl,thiophenyl, imidazolyl, oxazolyl, thiazolyl, pyrazolyl, pyridinyl,pyrimidinyl, quinolinyl, isoquinolinyl, purinyl, tetrazolyl, triazinyl,pyrazinyl, tetrazinyl, quinazolinyl, quinoxalinyl, thienyl, isoxazolyl,isothiazolyl, oxadiazolyl, thiadiazolyl, triazolyl, benzimidazolyl,benzoxazolyl, benzthiazolyl, benzisoxazolyl, benzisothiazolyl andcarbazoloyl, and the like.

As used herein, “hydroxy” or ““hydroxyl” refers to an —OH group.

As used herein, “alkoxy” refers to both an —O-(alkyl) or an—O-(unsubstituted cycloalkyl) group. Representative examples include,but are not limited to, methoxy, ethoxy, propoxy, butoxy,cyclopropyloxy, cyclobutyloxy, cyclopentyloxy, cyclohexyloxy, and thelike.

As used herein, “aryloxy” refers to an —O-aryl or an —O-heteroarylgroup. Representative examples include, but are not limited to, phenoxy,pyridinyloxy, furanyloxy, thienyloxy, pyrimidinyloxy, pyrazinyloxy, andthe like, and the like.

As used herein, “mercapto” refers to an —SH group.

As used herein, “alkylthio” refers to an —S-(alkyl) or an—S-(unsubstituted cycloalkyl) group. Representative examples include,but are not limited to, methylthio, ethylthio, propylthio, butylthio,cyclopropylthio, cyclobutylthio, cyclopentylthio, cyclohexylthio, andthe like.

As used herein, “arylthio” refers to an —S-aryl or an —S-heteroarylgroup. Representative examples include, but are not limited to,phenylthio, pyridinylthio, furanylthio, thienylthio, pyrimidinylthio,and the like.

As used herein, “halo” or “halogen” refers to fluorine, chlorine,bromine or iodine.

As used herein, “trihalomethyl” refers to a methyl group having threehalo substituents, such as a trifluoromethyl group.

As used herein, “cyano” refers to a —CN group.

As used herein, “sulfinyl” refers to a —S(O)R″ group, where R″ is any Rgroup as described in the various embodiments provided herein, or R″ maybe a hydroxyl group.

As used herein, “sulfonyl” refers to a —S(O)₂R″ group, where R″ is any Rgroup as described in the various embodiments provided herein, or R″ maybe a hydroxyl group.

As used herein, “S-sulfonamido” refers to a —S(O)₂NR″R″ group, where R″is any R group as described in the various embodiments provided herein.

As used herein, “N-sulfonamido” refers to a —NR″S(O)₂R″ group, where R″is any R group as described in the various embodiments provided herein.

As used herein, “O-carbamyl” refers to a —OC(O)NR″R″ group, where R″ isany R group as described in the various embodiments provided herein.

As used herein, “N-carbamyl” refers to an R″OC(O)NR″— group, where R″ isany R group as described in the various embodiments provided herein.

As used herein, “O-thiocarbamyl” refers to a —OC(S)NR″R″ group, where R″is any R group as described in the various embodiments provided herein.

As used herein, “N-thiocarbamyl” refers to a R″OC(S)NR″— group, where R″is any R group as described in the various embodiments provided herein.

As used herein, “amino” refers to an —NR″R″ group, where R″ is any Rgroup as described in the various embodiments provided herein.

As used herein, “C-amido” refers to a —C(O)NR″R″ group, where R″ is anyR group as described in the various embodiments provided herein.

As used herein, “N-amido” refers to a R″C(O)NR″— group, where R″ is anyR group as described in the various embodiments provided herein.

As used herein, “nitro” refers to a —NO₂ group.

As used herein, “bond” refers to a covalent bond.

As used herein, “optional” or “optionally” means that the subsequentlydescribed event or circumstance may but need not occur, and that thedescription includes instances where the event or circumstance occursand instances in which it does not. For example, “heterocycle groupoptionally substituted with an alkyl group” means that the alkyl may butneed not be present, and the description includes situations where theheterocycle group is substituted with an alkyl group and situationswhere the heterocycle group is not substituted with the alkyl group.

As used herein, “independently” means that the subsequently describedevent or circumstance is to be read on its own relative to other similarevents or circumstances. For example, in a circumstance where severalequivalent hydrogen groups are optionally substituted by another groupdescribed in the circumstance, the use of “independently optionally”means that each instance of a hydrogen atom on the group may besubstituted by another group, where the groups replacing each of thehydrogen atoms may be the same or different. Or for example, wheremultiple groups exist all of which can be selected from a set ofpossibilities, the use of “independently” means that each of the groupscan be selected from the set of possibilities separate from any othergroup, and the groups selected in the circumstance may be the same ordifferent.

As used herein, the term “pharmaceutically acceptable salt” refers tothose salts which counter ions which may be used in pharmaceuticals.Such salts include:

-   -   (1) acid addition salts, which can be obtained by reaction of        the free base of the parent conjugate with inorganic acids such        as hydrochloric acid, hydrobromic acid, nitric acid, phosphoric        acid, sulfuric acid, and perchloric acid and the like, or with        organic acids such as acetic acid, oxalic acid, (D) or (L) malic        acid, maleic acid, methane sulfonic acid, ethanesulfonic acid,        p-toluenesulfonic acid, salicylic acid, tartaric acid, citric        acid, succinic acid or malonic acid and the like; or    -   (2) salts formed when an acidic proton present in the parent        conjugate either is replaced by a metal ion, e.g., an alkali        metal ion, an alkaline earth ion, or an aluminum ion; or        coordinates with an organic base such as ethanolamine,        diethanolamine, triethanolamine, trimethamine,        N-methylglucamine, and the like.        Pharmaceutically acceptable salts are well known to those        skilled in the art, and any such pharmaceutically acceptable        salt may be contemplated in connection with the embodiments        described herein

As used herein, “amino acid” (a.k.a. “AA”) means any molecule thatincludes an alpha-carbon atom covalently bonded to an amino group and anacid group. The acid group may include a carboxyl group. “Amino acid”may include molecules having one of the formulas:

wherein R′ is a side group and Φ includes at least 3 carbon atoms.“Amino acid” includes stereoisomers such as the D-amino acid and L-aminoacid forms. Illustrative amino acid groups include, but are not limitedto, the twenty endogenous human amino acids and their derivatives, suchas lysine (Lys), asparagine (Asn), threonine (Thr), serine (Ser),isoleucine (Ile), methionine (Met), proline (Pro), histidine (His),glutamine (Gln), arginine (Arg), glycine (Gly), aspartic acid (Asp),glutamic acid (Glu), alanine (Ala), valine (Val), phenylalanine (Phe),leucine (Leu), tyrosine (Tyr), cysteine (Cys), tryptophan (Trp),phosphoserine (PSER), sulfo-cysteine, arginosuccinic acid (ASA),hydroxyproline, phosphoethanolamine (PEA), sarcosine (SARC), taurine(TAU), carnosine (CARN), citrulline (CIT), anserine (ANS),1,3-methyl-histidine (ME-HIS), alpha-amino-adipic acid (AAA),beta-alanine (BALA), ethanolamine (ETN), gamma-amino-butyric acid(GABA), beta-amino-isobutyric acid (BAIA), alpha-amino-butyric acid(BABA), L-allo-cystathionine (cystathionine-A; CYSTA-A), L-cystathionine(cystathionine-B; CYSTA-B), cystine, allo-isoleucine (ALLO-ILE),DL-hydroxylysine (hydroxylysine (I)), DL-allo-hydroxylysine(hydroxylysine (2)), omithine (ORN), homocystine (HCY), and derivativesthereof. It will be appreciated that each of these examples are alsocontemplated in connection with the present disclosure in theD-configuration as noted above. Specifically, for example, D-lysine(D-Lys), D-asparagine (D-Asn), D-threonine (D-Thr), D-serine (D-Ser),D-isoleucine (D-Ile), D-methionine (D-Met), D-proline (D-Pro),D-histidine (D-His), D-glutamine (D-Gln), D-arginine (D-Arg), D-glycine(D-Gly), D-aspartic acid (D-Asp), D-glutamic acid (D-Glu), D-alanine(D-Ala), D-valine (D-Val), D-phenylalanine (D-Phe), D-leucine (D-Leu),D-tyrosine (D-Tyr), D-cysteine (D-Cys), D-tryptophan (D-Trp),D-citrulline (D-CIT), D-carnosine (D-CARN), and the like. In connectionwith the embodiments described herein, amino acids can be covalentlyattached to other portions of the conjugates described herein throughtheir alpha-amino and carboxy functional groups (i.e. in a peptide bondconfiguration), or through their side chain functional groups (such asthe side chain carboxy group in glutamic acid) and either theiralpha-amino or carboxy functional groups. It will be understood thatamino acids, when used in connection with the conjugates describedherein, may exist as zwitterions in a conjugate in which they areincorporated.

As used herein, “sugar” refers to carbohydrates, such asmonosaccharides, disaccharides, or oligosaccharides. In connection withthe present disclosure, monosaccharides are preferred. Non-limitingexamples of sugars include erythrose, threose, ribose, arabinose,xylose, lyxose, allose, altrose, glucose, mannose, galactose, ribulose,fructose, sorbose, tagatose, and the like. It will be understood that asused in connection with the present disclosure, sugar includes cyclicisomers of amino sugars, deoxy sugars, acidic sugars, and combinationsthereof. Non-limiting examples of such sugars include, galactosamine,glucosamine, deoxyribose, fucose, rhamnose, glucuronic acid, ascorbicacid, and the like. In some embodiments, sugars for use in connectionwith the present disclosure include

As used herein, “prodrug” refers to a compound that can be administeredto a subject in a pharmacologically inactive form which then can beconverted to a pharmacologically active form through a normal metabolicprocess, such as hydrolysis of an oxazolidine. It will be understoodthat the metabolic processes through which a prodrug can be converted toan active drug include, but are not limited to, one or more spontaneouschemical reaction(s), enzyme-catalyzed chemical reaction(s), and/orother metabolic chemical reaction(s), or a combination thereof. It willbe appreciated that understood that a variety of metabolic processes areknown in the art, and the metabolic processes through which the prodrugsdescribed herein are converted to active drugs are non-limiting. Aprodrug can be a precursor chemical compound of a drug that has atherapeutic effect on a subject.

Au used herein, the term “therapeutically effective amount” refers to anamount of a drug or pharmaceutical agent that elicits the biological ormedicinal response in a subject (i.e. a tissue system, animal or human)that is being sought by a researcher, veterinarian, medical doctor orother clinician, which includes, but is not limited to, alleviation ofthe symptoms of the disease or disorder being treated. In one aspect,the therapeutically effective amount is that amount of an active whichmay treat or alleviate the disease or symptoms of the disease at areasonable benefit/risk ratio applicable to any medical treatment. Inanother aspect, the therapeutically effective amount is that amount ofan inactive prodrug which when converted through normal metabolicprocesses to produce an amount of active drug capable of eliciting thebiological or medicinal response in a subject that is being sought.

It is also appreciated that the dose, whether referring to monotherapyor combination therapy, is advantageously selected with reference to anytoxicity, or other undesirable side effect, that might occur duringadministration of one or more of the conjugates described herein.Further, it is appreciated that the co-therapies described herein mayallow for the administration of lower doses of conjugates that show suchtoxicity, or other undesirable side effect, where those lower doses arebelow thresholds of toxicity or lower in the therapeutic window thanwould otherwise be administered in the absence of a cotherapy.

As used herein, “administering” includes all means of introducing theconjugates and compositions described herein to the host animal,including, but are not limited to, oral (po), intravenous (iv),intramuscular (im), subcutaneous (sc), transdermal, inhalation, buccal,ocular, sublingual, vaginal, rectal, and the like. The conjugates andcompositions described herein may be administered in unit dosage formsand/or formulations containing conventional nontoxicpharmaceutically-acceptable carriers, adjuvants, and/or vehicles.

As used herein “pharmaceutical composition” or “composition” refers to amixture of one or more of the conjugates described herein, orpharmaceutically acceptable salts, solvates, hydrates thereof, withother chemical components, such as pharmaceutically acceptableexcipients. The purpose of a pharmaceutical composition is to facilitateadministration of a conjugate to a subject. Pharmaceutical compositionssuitable for the delivery of conjugates described and methods for theirpreparation will be readily apparent to those skilled in the art. Suchcompositions and methods for their preparation may be found, forexample, in ‘Remington's Pharmaceutical Sciences’, 19th Edition (MackPublishing Company, 1995).

A “pharmaceutically acceptable excipient” refers to an inert substanceadded to a pharmaceutical composition to further facilitateadministration of a conjugate such as a diluent or a carrier.

DETAILED DESCRIPTION

In each of the foregoing and each of the following embodiments, it is tobe understood that the formulae include and represent not only allpharmaceutically acceptable salts of the conjugates, but also includeany and all hydrates and/or solvates of the conjugate formulae. It isappreciated that certain functional groups, such as the hydroxy, amino,and like groups form complexes and/or coordination conjugates with waterand/or various solvents, in the various physical forms of theconjugates. Accordingly, the above formulae are to be understood toinclude and represent those various hydrates and/or solvates. It is alsoto be understood that the non-hydrates and/or non-solvates of theconjugate formulae are described by such formula, as well as thehydrates and/or solvates of the conjugate formulae.

The conjugates described herein can be expressed by the generalizeddescriptors B, L and Drug, where B is a cell surface receptor bindingligand (a.k.a. a “binding ligand”), L is a linker that may include areleasable portion (i.e. a releasable linker) and L may be described byone or more of the groups AA, L¹, L², L³, L⁴ or L⁵ as defined herein,and Drug represents one or more drugs (e.g. D¹ and D²) covalentlyattached to the conjugate.

The conjugates described herein can be described according to variousembodiments including but not limited to

-   -   B-(AA)_(z1)-L²-(L³)_(z2)-(AA)_(z3)-(L¹)_(z4)-(L⁴)_(z5)-D¹-L⁵-D²    -   B-L¹-AA-L¹-AA-L¹-L²-(L³)_(z6)-(L⁴)_(z7)-(AA)^(z8)-(L⁴)_(z9)-D¹-L⁵-D²    -   B-(AA)_(z10)-L²-D²    -   B-(AA)_(z11)-L²-D¹-L⁵-D¹-L²-(AA)_(z12)-B    -   B-(AA)₄-L²-D¹-L⁵-D²    -   B-(AA)₄-L²-L³-AA-L¹-L⁴-D¹-L⁵-D²    -   B-(AA)₄-L²-L³-(AA)₂-D¹-L⁵-D²    -   B-(AA)₄-L²-D²    -   B-(AA)₄-L²-D¹-L⁵-D¹-L²-(AA)₄-B    -   B-L¹-AA-L¹-AA-L¹-L²-D-L⁵-D²    -   B-L1-AA-L1-AA-L1-L2-L3-(AA)₂-L4-D1-L5-D2    -   B-L¹-AA-L¹-AA-L¹-L²-L³-L⁴-(AA)₂-L⁴-D¹-L⁵-D²    -   B-L¹-AA-L¹-AA-L¹-L²-L³-L⁴-D¹-L⁵-D²    -   B-L¹-AA-L¹-AA-L¹-L²-L³-(AA)₂-D¹-L⁵-D²    -   B-L¹-AA-L¹-AA-L¹-L²-L³-D¹-L⁵-D²        wherein B, AA, L¹, L², L³, L⁴, L⁵, D¹ and D² are defined by the        various embodiments described herein, and z1 is 2, 3, 4 or 5; z2        is 0, 1 or 2; z3 is 0, 1, 2, 3 or 4; z4 is 0, 1 or 2; z5 is 0, 1        or 2; y1 is 0, 1 or 2; y2 is 0, 1 or 2; y3 is 0, 1, 2, 3 or 4;        and y4 is 0, 1 or 2.

As used herein, the term cell surface receptor binding ligand (aka a“binding ligand”), generally refers to compounds that bind to and/ortarget receptors that are found on cell surfaces, and in particularthose that are found on, over-expressed by, and/or preferentiallyexpressed on the surface of pathogenic cells. Illustrative ligandsinclude, but are not limited to, vitamins and vitamin receptor bindingcompounds.

Illustrative vitamin moieties include carnitine, inositol, lipoic acid,pyridoxal, ascorbic acid, niacin, pantothenic acid, folic acid,riboflavin, thiamine, biotin, vitamin B₁₂, and the lipid solublevitamins A, D, E and K. These vitamins, and their receptor-bindinganalogs and derivatives, constitute the targeting entity covalentlyattachment to the linker. Illustrative biotin analogs that bind tobiotin receptors include, but are not limited to, biocytin, biotinsulfoxide, oxybiotin, and the like).

In some embodiments, the B is folate or derivative thereof. In someembodiments, the B is of the formula I

wherein

R¹ and R² in each instance are independently selected from the groupconsisting of H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,—OR⁷, —SR⁷ and —NR⁷R^(7′), wherein each hydrogen atom in C₁-C₆ alkyl,C₂-C₆ alkenyl and C₂-C₆ alkynyl is independently optionally substitutedby halogen, —OR⁸, —SR⁸, —NR⁸R^(8′), —C(O)R⁸, —C(O)OR⁸ or —C(O)NR⁸R^(8′);

R³, R⁴, R⁵ and R⁶ are each independently selected from the groupconsisting of H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,—CN, —NO₂, —NCO, —OR⁹, —SR⁹, —NR⁹R^(9′), —C(O)R⁹, —C(O)OR⁹ and—C(O)NR⁹R^(9′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyland C₂-C₆ alkynyl is independently optionally substituted by halogen,—OR¹⁰, —SR¹⁰, —NR¹⁰R^(10′), —C(O)R¹⁰, —C(O)OR¹⁰ or —C(O)NR¹⁰R^(10′);

each R⁷, R^(7′), R⁸, R^(8′), R⁹, R^(9′), R¹⁰ and R^(10′) isindependently H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl or C₂-C₆ alkynyl;

X¹ is —NR¹¹—, ═N—, —N═, —C(R¹¹)═ or ═C(R¹¹)—;

X² is —NR^(11′)— or ═N—;

X³ is —NR^(11″)—, —N═ or —C(R^(11′))═;

X⁴ is —N═ or —C═;

X⁵ is NR¹² or CR¹²R^(12′);

Y¹ is H, D, —OR¹³, —SR¹³ or —NR¹³R^(13′) when X¹ is —N═ or —C(R¹¹)═, orY¹ is ═O when X¹ is —NR¹¹—, ═N— or ═C(R¹¹)—;

Y² is H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, —C(O)R¹⁴, —C(O)OR¹⁴,—C(O)NR¹⁴R^(14′) when X⁴ is —C═, or Y² is absent when X⁴ is —N═;

R¹¹, R^(11′), R^(11″), R¹², R^(12′), R¹³, R^(13′), R¹⁴ and R^(14′) areeach independently selected from the group consisting of H, D, C₁-C₆alkyl, —C(O)R¹⁵, —C(O)OR¹⁵ and —C(O)NR¹⁵R^(15′);

R¹⁵ and R^(15′) are each independently H or C₁-C₆ alkyl;

m is 1, 2, 3 or 4; and

* is a covalent bond.

It will be appreciate that when B is described according to the formulaI, that both the D- and L-forms are contemplated. In some embodiments, Bis of the formula Ia or Ib

where each of R¹, R², R³, R⁴, R⁵, R⁶, Y¹, Y², X¹, X², X³, X⁴, X⁵, mand * are as defined for the formula I.

In some embodiments described herein, R¹ and R² are H. In someembodiments described herein, m is 1. In some embodiments describedherein, R³ is H. In some embodiments described herein, R⁴ is H. In someembodiments described herein, R⁵ is H. In some embodiments describedherein, R⁶ is H. In some embodiments described herein, R³, R⁴, R⁵ and R⁶are H. In some embodiments described herein, X¹ is —NR¹¹, and R¹¹ is H.In some embodiments described herein, X² is ═N—. In some embodimentsdescribed herein, X³ is —N═. In some embodiments described herein, X⁴ is—N═. In some embodiments described herein, XI is —NR¹, and R¹¹ is H; X²is ═N—; X³ is —N═; and X⁴ is —N═. In some embodiments described herein,X⁵ is NR¹², and R¹² is H. In some embodiments, Y¹ is ═O. In someembodiments, Y² is absent. In some embodiments, B is of the formula Ic

wherein * is defined for formula I.

In some embodiments, B is of the formula Id

wherein * is defined for formula I.

It will be appreciated that in certain embodiments, the conjugatesdescribed herein can be represented by the exemplary formulae

or a pharmaceutically acceptable salt thereof.

The linker for connected B and Drug in the conjugates described hereincan be represented by the groups AA, L¹, L², L³, L⁴ or L⁵.

AA is an amino acid as defined herein. In certain embodiments, AA is anaturally occurring amino acid. In certain embodiments, AA is in theL-form. In certain embodiments, AA is in the D-form. It will beappreciated that in certain embodiments, the conjugates described hereinwill comprise more than one amino acid as portions of the linker, andthe amino acids can be the same or different, and can be selected from agroup of amino acids. It will be appreciated that in certainembodiments, the conjugates described herein will comprise more than oneamino acid as portions of the linker, and the amino acids can be thesame or different, and can be selected from a group of amino acids in D-or L-form. In some embodiments, each AA is independently selected fromthe group consisting of L-lysine, L-asparagine, L-threonine, L-serine,L-isoleucine, L-methionine, L-proline, L-histidine, L-glutamine,L-arginine, L-glycine, L-aspartic acid, L-glutamic acid, L-alanine,L-valine, L-phenylalanine, L-leucine, L-tyrosine, L-cysteine,L-tryptophan, L-phosphoserine, L-sulfo-cysteine, L-arginosuccinic acid,L-hydroxyproline, L-phosphoethanolamine, L-sarcosine, L-taurine,L-carnosine, L-citrulline, L-anserine, L-1,3-methyl-histidine,L-alpha-amino-adipic acid, D-lysine, D-asparagine, D-threonine,D-serine, D-isoleucine, D-methionine, D-proline, D-histidine,D-glutamine, D-arginine, D-glycine, D-aspartic acid, D-glutamic acid,D-alanine, D-valine, D-phenylalanine, D-leucine, D-tyrosine, D-cysteine,D-tryptophan, D-citrulline and D-carnosine.

In some embodiments, each AA is independently selected from the groupconsisting of L-asparagine, L-arginine, L-glycine, L-aspartic acid,L-glutamic acid, L-glutamine, L-cysteine, L-alanine, L-valine,L-leucine, L-isoleucine, L-citrulline, D-asparagine, D-arginine,D-glycine, D-aspartic acid, D-glutamic acid, D-glutamine, D-cysteine,D-alanine, D-valine, D-leucine, D-isoleucine and D-citrulline. In someembodiments, each AA is independently selected from the group consistingof Asp, Arg, Val, Ala, Cys and CIT. In some embodiments, each AA isindependently selected from the group consisting of Asp, Arg, Val, Ala,D-Cys and CIT. In some embodiments, each AA is independently selectedfrom the group consisting of Asp, Arg, Val, Ala and CIT. In someembodiments, z1 is 4 and the sequence of AA therein is-Asp-Arg-Asp-Asp-. In some embodiments, z3 is 2 and the sequence of AAtherein is Val-Ala. In some embodiments, z3 is 2 and the sequence of AAtherein is Val-CIT. In some embodiments, z1 is 4 and the sequence of AAtherein is -Asp-Arg-Asp-Asp-, and z3 is 2 and the sequence of AA thereinis Val-Ala. In some embodiments, z1 is 4 and the sequence of AA thereinis -Asp-Arg-Asp-Asp-, and z3 is 2 and the sequence of AA therein isVal-CIT.

In some embodiments, z8 is 3. In some embodiments, z8 is 2. In someembodiments, z8 is 2, and the sequence of AA therein is Val-Ala. In someembodiments, z10 is 5. In some embodiments, z10 is 4. In someembodiments, z10 is 3. In some embodiments, z10 is 4 and the sequence ofAA therein is -Asp-Arg-Asp-Asp-. In some embodiments, z11 is 5. In someembodiments, z11 is 4. In some embodiments, z11 is 3. In someembodiments, z11 is 4 and the sequence of AA therein is-Asp-Arg-Asp-Asp-. In some embodiments, z12 is 5. In some embodiments,z12 is 4. In some embodiments, z12 is 3. In some embodiments, z12 is 4and the sequence of AA therein is -Asp-Asp-Arg-Asp-. In someembodiments, z11 is 4 and z12 is 4. In some embodiments, z11 is 4 andthe sequence of AA therein is -Asp-Arg-Asp-Asp-, and z12 is 4 and thesequence of AA therein is -Asp-Asp-Arg-Asp-. In some embodiments, z8 is2, and the sequence of AA is -Glu-Glu-, wherein the amino acids arecovalently attached at their alpha-amino functionality and their sidechain carboxylate.

L¹ can be present or absent in the conjugates described herein. When L¹is present, L¹ can be any group covalently attaching portions of thelinker to the binding ligand, portions of the linker to one another, orto D¹, or to D². It will be understood that the structure of L¹ is notparticularly limited in any way. It will be further understood that L¹can comprise numerous functionalities well known in the art tocovalently attach portions of the linker to the binding ligand, portionsof the linker to one another, or to D¹, or to D², including but notlimited to, alkyl groups, ether groups, amide groups, carboxy groups,sulfonate groups, alkenyl groups, alkynyl groups, cycloalkyl groups,aryl groups, heterocycloalkyl, heteroaryl groups, and the like. In someembodiments, L¹ is a linker of the formula II

wherein

R¹⁶ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, —C(O)R¹⁹, —C(O)OR¹⁹ and —C(O)NR¹⁹R^(19′),wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl and C₂-C₆alkynyl is independently optionally substituted by halogen, C₁-C₆ alkyl,C₂-C₆ alkenyl, and C₂-C₆ alkynyl, —OR²⁰, —OC(O)R²⁰, —OC(O)NR²⁰R^(20′),—OS(O)R²⁰, —OS(O)₂R²⁰, —SR²⁰, —S(O)R²⁰, —S(O)₂R²⁰, —S(O)NR²⁰R^(20′),—S(O)₂NR²⁰R^(20′), —OS(O)NR²⁰R^(20′), —OS(O)₂NR²⁰R^(20′), —NR²⁰R^(20′),—NR²⁰C(O)R²¹, —NR²⁰C(O)OR²¹, —NR²⁰C(O)NR²¹R^(21′), —NR²⁰S(O)R²¹,—NR²⁰S(O)₂R²¹, —NR²⁰S(O)NR²¹R^(21′), —NR²⁰S(O)₂NR²¹R^(21′), —C(O)R²⁰,—C(O)OR²⁰ or —C(O)NR²⁰R^(20′);

each R¹⁷ and R^(17′) is independently selected from the group consistingof H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR²², —OC(O)R²², —OC(O)NR²²R^(22′), —OS(O)R²²,—OS(O)₂R²², —SR²², —S(O)R²², —S(O)₂R²², —S(O)NR²²R^(22′),—S(O)₂NR²²R^(22′), —OS(O)NR²²R^(22′), —OS(O)₂NR²²R^(22′), —NR²²R^(22′),—NR²²C(O)R²³, —NR²²C(O)OR²³, —NR²²C(O)NR²³R^(23′), —NR²²S(O)R²³,—NR²²S(O)₂R²³, —NR²²S(O)NR²³R^(23′), —NR²²S(O)₂NR²³R^(23′), —C(O)R²²,—C(O)OR²², and —C(O)NR²²R^(22′), wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, —OR²⁴, —OC(O)R²⁴, —OC(O)NR²⁴R^(24′), —OS(O)R²⁴,—OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴, —S(O)₂R²⁴, —S(O)NR²⁴R^(24′),—S(O)₂NR²⁴R^(24′), —OS(O)NR²⁴R^(24′), —OS(O)₂NR²⁴R^(24′), —NR²⁴R^(24′),—NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵, —NR²⁴C(O)NR²⁵R^(25′), —NR²⁴S(O)R²⁵,—NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^(25′), —NR²⁴S(O)₂NR²⁵R^(25′), —C(O)R²⁴,—C(O)OR²⁴ or —C(O)NR²⁴R^(24′); or R¹⁷ and R^(17′) may combine to form aC₄-C₆ cycloalkyl or a 4- to 6-membered heterocycle, wherein eachhydrogen atom in C₄-C₆ cycloalkyl or 4- to 6-membered heterocycle isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR²⁴,—OC(O)R²⁴, —OC(O)NR²⁴R^(24′), —OS(O)R²⁴, —OS(O)₂R²⁴, —SR²⁴, —S(O)R²⁴,—S(O)₂R²⁴, —S(O)NR²⁴R^(24′), —S(O)₂NR²⁴R^(24′), —OS(O)NR²⁴R^(24′),—OS(O)₂NR²⁴R^(24′), —NR²⁴R^(24′), —NR²⁴C(O)R²⁵, —NR²⁴C(O)OR²⁵,—NR²⁴C(O)NR²⁵R^(25′), —NR²⁴S(O)R²⁵, —NR²⁴S(O)₂R²⁵, —NR²⁴S(O)NR²⁵R^(25′),—NR²⁴S(O)₂NR²⁵R^(25′), —C(O)R²⁴, —C(O)OR²⁴ or —C(O)NR²⁴R^(24′);

R¹⁸ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR²⁶,—OC(O)R²⁶, —OC(O)NR²⁶R^(26′), —OS(O)R²⁶, —OS(O)₂R²⁶, —SR²⁶, —S(O)R²⁶,—S(O)₂R²⁶, —S(O)NR²⁶R^(26′), —S(O)₂NR²⁶R^(26′), —OS(O)NR²⁶R^(26′),—OS(O)₂NR²⁶R^(26′), —NR²⁶R^(26′), —NR²⁶C(O)R²⁷, —NR²⁶C(O)OR²⁷,—NR²⁶C(O)NR²⁷R^(27′), —NR²⁶C(═NR^(26″))NR²⁷R^(27′), —NR²⁶S(O)R²⁷,—NR²⁶S(O)₂R²⁷, —NR²⁶S(O)NR²⁷R^(27′), —NR²⁶S(O)₂NR²⁷R^(27′), —C(O)R²⁶,—C(O)OR²⁶ and —C(O)NR²⁶R^(26′), wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, —(CH₂)_(p)OR²⁸, —(CH₂)_(p)(OCH₂)_(q)OR²⁸,—(CH₂)_(p)(OCH₂CH₂)_(q)OR²⁸, —OR²⁹, —OC(O)R²⁹, —OC(O)NR²⁹R^(29′),—OS(O)R²⁹, —OS(O)₂R²⁹, —(CH₂)_(p)OS(O)₂₀R²⁹, —OS(O)₂₀R²⁹, —SR²⁹,—S(O)R²⁹, —S(O)₂R²⁹, —S(O)NR²⁹R^(29′), —S(O)₂NR²⁹R^(29′),—OS(O)NR²⁹R^(29′), —OS(O)₂NR²⁹R^(29′), —NR²⁹R^(29′), —NR²⁹C(O)R³⁰,—NR²⁹C(O)OR³⁰, —NR²⁹C(O)NR³⁰R^(30′), —NR²⁹S(O)R³⁰, —NR²⁹S(O)₂R³⁰,—NR²⁹S(O)NR³⁰R^(30′), —NR²⁹S(O)₂NR³⁰R^(30′), —C(O)R²⁹, —C(O)OR²⁹ or—C(O)NR²⁹R^(29′);

each R¹⁹, R^(19′), R²⁰, R^(20′), R²¹, R^(21′), R²², R^(22′), R²³,R^(23′), R²⁴, R^(24′), R²⁵, R^(25′), R²⁶, R^(26′), R^(26″), R²⁹,R^(29′), R³⁰ and R^(30′) is independently selected from the groupconsisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl, wherein each hydrogen atom in C₁-C₇ alkyl, C₂-C₇alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, or 5- to 7-membered heteroaryl isindependently optionally substituted by halogen, —OH, —SH, —NH₂ or—CO₂H;

R²⁷ and R^(27′) are each independently selected from the groupconsisting of H, C₁-C₉ alkyl, C₂-C₉ alkenyl, C₂-C₉ alkynyl, C₃-C₆cycloalkyl, —(CH₂)_(p)(sugar), —(CH₂)_(p)(OCH₂CH₂)_(q)-(sugar) and—(CH₂)_(p)(OCH₂CH₂CH₂)_(q)(sugar);

R²⁸ is a H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5; and

* is a covalent bond.

It will be appreciate that when L¹ is described according to the formulaII, that both the R- and S-configurations are contemplated. In someembodiments, L¹ is of the formula IIa or IIb

where each of R¹⁶, R¹⁷, R^(17′), R¹⁸, n and * are as defined for theformula II.

In some embodiments, each L¹ is selected from the group consisting of

and combinations thereof,wherein

R¹⁶ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, —C(O)R¹⁹, —C(O)OR¹⁹ and —C(O)NR¹⁹R^(19′),wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl and C₂-C₆alkynyl is independently optionally substituted by halogen, C₁-C₆ alkyl,C₂-C₆ alkenyl, and C₂-C₆ alkynyl, —OR²⁰, —OC(O)R²⁰, —OC(O)NR²⁰R^(20′),—OS(O)R²⁰, —OS(O)₂R²⁰, —SR²⁰, —S(O)R²⁰, —S(O)₂R²⁰, —S(O)NR²⁰R^(20′),—S(O)₂NR²⁰R^(20′), —OS(O)NR²⁰R^(20′), —OS(O)₂NR²⁰R^(20′), —NR²⁰R^(20′),—NR²⁰C(O)R²¹, —NR²⁰C(O)OR²¹, —NR²⁰C(O)NR²¹R^(21′), —NR²⁰S(O)R²¹,—NR²⁰S(O)₂R²¹, —NR²⁰S(O)NR²¹R^(21′), —NR²⁰S(O)₂NR²¹R^(21′), —C(O)R²⁰,—C(O)OR²⁰ or —C(O)NR²⁰R^(20′);

R¹⁸ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR²⁶,—OC(O)R²⁶, —OC(O)NR²⁶R^(26′), —OS(O)R²⁶, —OS(O)₂R²⁶, —SR²⁶, —S(O)R²⁶,—S(O)₂R²⁶, —S(O)NR²⁶R^(26′), —S(O)₂NR²⁶R^(26′), —OS(O)NR²⁶R^(26′),—OS(O)₂NR²⁶R^(26′), —NR²⁶R^(26′), —NR²⁶C(O)R²⁷, —NR²⁶C(O)OR²⁷,—NR²⁶C(O)NR²⁷R^(27′), —NR²⁶C(═NR^(26″))NR²⁷R^(27′), —NR²⁶S(O)R²⁷,—NR²⁶S(O)₂R²⁷, —NR²⁶S(O)NR²⁷R^(27′), —NR²⁶S(O)₂NR²⁷R^(27′), —C(O)R²⁶,—C(O)OR²⁶ and —C(O)NR²⁶R^(26′), wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, —(CH₂)_(p)OR²⁸, —(CH₂)_(p)(OCH₂)_(q)OR²⁸,—(CH₂)_(p)(OCH₂CH₂)_(q)OR²⁸, —OR²⁹, —OC(O)R²⁹, —OC(O)NR²⁹R^(29′),—OS(O)R²⁹, —OS(O)₂R²⁹, —(CH₂)_(p)OS(O)₂₀R²⁹, —OS(O)₂₀R²⁹, —SR²⁹,—S(O)R²⁹, —S(O)₂R²⁹, —S(O)NR²⁹R^(29′), —S(O)₂NR²⁹R^(29′),—OS(O)NR²⁹R^(29′), —OS(O)₂NR²⁹R^(29′), —NR²⁹R^(29′), —NR²⁹C(O)R³⁰,—NR²⁹C(O)OR³⁰, —NR²⁹C(O)NR³⁰R^(30′), —NR²⁹S(O)R³⁰, —NR²⁹S(O)₂R³⁰,—NR²⁹S(O)NR³⁰R^(30′), —NR²⁹S(O)₂NR³⁰R^(30′), —C(O)R²⁹, —C(O)OR²⁹ or—C(O)NR²⁹R^(29′);

each R¹⁹, R^(19′), R²⁰, R^(20′), R²¹, R^(21′), R²⁶, R^(26′), R^(26″),R²⁹, R^(29′), R³⁰ and R^(30′) is independently selected from the groupconsisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl, wherein each hydrogen atom in C₁-C₇ alkyl, C₂-C₇alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, or 5- to 7-membered heteroaryl isindependently optionally substituted by halogen, —OH, —SH, —NH₂ or—CO₂H;

R²⁷ and R^(27′) are each independently selected from the groupconsisting of H, C₁-C₉ alkyl, C₂-C₉ alkenyl, C₂-C₉ alkynyl, C₃-C₆cycloalkyl, —(CH₂)_(p)(sugar), —(CH₂)_(p)(OCH₂CH₂)_(q)-(sugar) and—(CH₂)_(p)(OCH₂CH₂CH₂)_(q)(sugar);

R²⁸ is H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5; and

* is a covalent bond.

In some embodiments, each L¹ is selected from the group consisting of

wherein R¹⁶ is defined as described herein, and * is a covalent bond.

In some embodiments, R¹⁶ is H. In some embodiments, R¹⁸ is selected fromthe group consisting of H, 5- to 7-membered heteroaryl, —OR²⁶,—NR²⁶C(O)R²⁷, —NR²⁶C(O)NR²⁷R^(27′), —NR²⁶C(═NR^(26″))NR²⁷R^(27′), and—C(O)NR²⁶R^(26′), wherein each hydrogen atom 5- to 7-membered heteroarylis independently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, —(CH₂)_(p)OR²⁸, —(CH₂)_(p)(OCH₂)_(q)OR²⁸,—(CH₂)_(p)(OCH₂CH₂)_(q)OR²⁸, —OR²⁹, —OC(O)R²⁹, —OC(O)NR²⁹R^(29′),—OS(O)R²⁹, —OS(O)₂R²⁹, —(CH₂)_(p)OS(O)₂₀R²⁹, —OS(O)₂OR²⁹, —SR²⁹,—S(O)R²⁹, —S(O)₂R²⁹, —S(O)NR²⁹R^(29′), —S(O)₂NR²⁹R^(29′),—OS(O)NR²⁹R^(29′), —OS(O)₂NR²⁹R^(29′), —NR²⁹R^(29′), —NR²⁹C(O)R³⁰,—NR²⁹C(O)OR³⁰, —NR²⁹C(O)NR³⁰R^(30′), —NR²⁹S(O)R³⁰, —NR²⁹S(O)₂R³⁰,—NR²⁹S(O)NR³⁰R^(30′), —NR²⁹S(O)₂NR³⁰R^(30′), —C(O)R²⁹, —C(O)OR²⁹ or—C(O)NR²⁹R^(29′);

each R²⁶, R^(26′), R^(26″), R²⁹, R^(29′), R³⁰ and R^(30′) isindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl, whereineach hydrogen atom in C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, or 5- to7-membered heteroaryl is independently optionally substituted byhalogen, —OH, —SH, —NH₂ or —CO₂H;

R²⁷ and R^(27′) are each independently selected from the groupconsisting of H, C₁-C₉ alkyl, C₂-C₉ alkenyl, C₂-C₉ alkynyl, C₃-C₆cycloalkyl, —(CH₂)_(p)(sugar), —(CH₂)_(p)(OCH₂CH₂)_(q)-(sugar) and—(CH₂)_(p)(OCH₂CH₂CH₂)_(q)(sugar);

R²⁸ is a H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5; and

* is a covalent bond.

In some embodiments, R¹⁸ is selected from the group consisting of H, 5-to 7-membered heteroaryl, —OR²⁶, —NR²⁶C(O)R²⁷, —NR²⁶C(O)NR²⁷R^(27′),—NR²⁶C(═NR^(26″))NR²⁷R^(27′), and —C(O)NR²⁶R^(26′), wherein eachhydrogen atom 5- to 7-membered heteroaryl is independently optionallysubstituted by —(CH₂)_(p)OR²⁸, —OR²⁹, —(CH₂)_(p)OS(O)₂₀R²⁹ and—OS(O)₂₀R²⁹,

each R²⁶, R^(26′), R^(26″) and R²⁹ is independently H or C₁-C₇ alkyl,wherein each hydrogen atom in C₁-C₇ alkyl is independently optionallysubstituted by halogen, —OH, —SH, —NH₂ or —CO₂H;

R²⁷ and R^(27′) are each independently selected from the groupconsisting of H, —(CH₂)_(p)(sugar), —(CH₂)_(p)(OCH₂CH₂)_(q)(sugar) and—(CH₂)_(p)(OCH₂CH₂CH₂)_(q)(sugar);

R²⁸ is H or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5; and

* is a covalent bond.

In some embodiments, each L¹ is selected from the group consisting of

and combinations thereof,

wherein

R¹⁸ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR²⁶,—OC(O)R²⁶, —OC(O)NR²⁶R^(26′), —OS(O)R²⁶, —OS(O)₂R²⁶, —SR²⁶, —S(O)R²⁶,—S(O)₂R²⁶, —S(O)NR²⁶R^(26′), —S(O)₂NR²⁶R^(26′), —OS(O)NR²⁶R^(26′),—OS(O)₂NR²⁶R^(26′), —NR²⁶R^(26′), —NR²⁶C(O)R²⁷, —NR²⁶C(O)OR²⁷,—NR²⁶C(O)NR²⁷R^(27′), —NR²⁶C(═NR²⁶)NR²⁷R^(27′), —NR²⁶S(O)R²⁷,—NR²⁶S(O)₂R²⁷, —NR²⁶S(O)NR²⁷R^(27′), —NR²⁶S(O)₂NR²⁷R^(27′), —C(O)R²⁶,—C(O)OR²⁶ and —C(O)NR²⁶R^(26′), wherein each hydrogen atom in C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, —(CH₂)_(p)OR²⁸, —(CH₂)_(p)(OCH₂)_(q)OR²⁸,—(CH₂)_(p)(OCH₂CH₂)_(q)OR²⁸, —OR²⁹, —OC(O)R²⁹, —OC(O)NR²⁹R^(29′),—OS(O)R²⁹, —OS(O)₂R²⁹, —(CH₂)_(p)OS(O)₂₀R²⁹, —OS(O)₂OR²⁹, —SR²⁹,—S(O)R²⁹, —S(O)₂R²⁹, —S(O)NR²⁹R^(29′), —S(O)₂NR²⁹R^(29′),—OS(O)NR²⁹R^(29′), —OS(O)₂NR²⁹R^(29′), —NR²⁹R^(29′), —NR²⁹C(O)R³⁰,—NR²⁹C(O)OR³⁰, —NR²⁹C(O)NR³⁰R^(30′), —NR²⁹S(O)R³⁰, —NR²⁹S(O)₂R³⁰,—NR²⁹S(O)NR³⁰R^(30′), —NR²⁹S(O)₂NR³⁰R^(30′), —C(O)R²⁹, —C(O)OR²⁹ or—C(O)NR²⁹R^(29′);

each R²⁶, R^(26′), R^(26″), R²⁹, R^(29′), R³⁰ and R^(30′) isindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl, whereineach hydrogen atom in C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, or 5- to7-membered heteroaryl is independently optionally substituted byhalogen, —OH, —SH, —NH₂ or —CO₂H;

R²⁷ and R^(27′) are each independently selected from the groupconsisting of H, C₁-C₉ alkyl, C₂-C₉ alkenyl, C₂-C₉ alkynyl, C₃-C₆cycloalkyl, —(CH₂)_(p)(sugar), —(CH₂)_(p)(OCH₂CH₂)_(q)-(sugar) and—(CH₂)_(p)(OCH₂CH₂CH₂)_(q)(sugar);

R²⁸ is a H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5; and

* is a covalent bond.

In some embodiments, R¹⁸ is selected from the group consisting of H, 5-to 7-membered heteroaryl, —OR²⁶, —NR²⁶C(O)R²⁷, —NR²⁶C(O)NR²⁷R^(27′),—NR²⁶C(═NR^(26″))NR²⁷R^(27′), and —C(O)NR²⁶R^(26′), wherein eachhydrogen atom 5- to 7-membered heteroaryl is independently optionallysubstituted by halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, —(CH₂)_(p)OR²⁸,—(CH₂)_(p)(OCH₂)_(q)OR²⁸, —(CH₂)_(p)(OCH₂CH₂)_(q)OR²⁸, —OR²⁹, —OC(O)R²⁹,—OC(O)NR²⁹R^(29′), —OS(O)R²⁹, —OS(O)₂R²⁹, —(CH₂)_(p)OS(O)₂₀R²⁹,—OS(O)₂₀R²⁹, —SR²⁹, —S(O)R²⁹, —S(O)₂R²⁹, —S(O)NR²⁹R^(29′),—S(O)₂NR²⁹R^(29′), —OS(O)NR²⁹R^(29′), —OS(O)₂NR²⁹R^(29′), —NR²⁹R^(29′),—NR²⁹C(O)R³⁰, —NR²⁹C(O)OR³⁰, —NR²⁹C(O)NR³⁰R^(30′), —NR²⁹S(O)R³⁰,—NR²⁹S(O)₂R³⁰, —NR²⁹S(O)NR³⁰R^(30′), —NR²⁹S(O)₂NR³⁰R^(30′), —C(O)R²⁹,—C(O)OR²⁹ or —C(O)NR²⁹R^(29′);

each R²⁶, R^(26′), R^(26″), R²⁹, R^(29′), R³⁰ and R^(30′) isindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl, whereineach hydrogen atom in C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, or 5- to7-membered heteroaryl is independently optionally substituted byhalogen, —OH, —SH, —NH₂ or —CO₂H;

R²⁷ and R^(27′) are each independently selected from the groupconsisting of H, C₁-C₉ alkyl, C₂-C₉ alkenyl, C₂-C₉ alkynyl, C₃-C₆cycloalkyl, —(CH₂)_(p)(sugar), —(CH₂)_(p)(OCH₂CH₂)_(q)-(sugar) and—(CH₂)_(p)(OCH₂CH₂CH₂)_(q)(sugar);

R²⁸ is a H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5; and

* is a covalent bond.

In some embodiments, R¹⁸ is selected from the group consisting of H, 5-to 7-membered heteroaryl, —OR²⁶, —NR²⁶C(O)R²⁷, —NR²⁶C(O)NR²⁷R^(27′),—NR²⁶C(═NR^(26″))NR²⁷R^(27′), and —C(O)NR²⁶R^(26′), wherein eachhydrogen atom 5- to 7-membered heteroaryl is independently optionallysubstituted by —(CH₂)_(p)OR²⁸, —OR²⁹, —(CH₂)_(p)OS(O)₂₀R²⁹ and—OS(O)₂₀R²⁹,

each R²⁶, R^(26′), R^(26″) and R²⁹ is independently H or C₁-C₇ alkyl,wherein each hydrogen atom in C₁-C₇ alkyl is independently optionallysubstituted by halogen, —OH, —SH, —NH₂ or —CO₂H;

R²⁷ and R^(27′) are each independently selected from the groupconsisting of H, —(CH₂)_(p)(sugar), —(CH₂)_(p)(OCH₂CH₂)_(q)(sugar) and—(CH₂)_(p)(OCH₂CH₂CH₂)_(q)(sugar);

R²⁸ is H or sugar;

n is 1, 2, 3, 4 or 5;

p is 1, 2, 3, 4 or 5;

q is 1, 2, 3, 4 or 5; and

* is a covalent bond.

In some embodiments of the conjugates described herein, L¹ is present.In some embodiments of the conjugates described herein, L¹ is absent. Insome embodiments, z4 is 0. In some embodiments, z4 is 1. In someembodiments, z4 is 2.

L² is a releasable linker. As used herein, the term “releasable linker”refers to a linker that includes at least one bond that can be brokenunder physiological conditions, such as a pH-labile, acid-labile,base-labile, oxidatively labile, metabolically labile, biochemicallylabile, or enzyme-labile bond. It is appreciated that such physiologicalconditions resulting in bond breaking do not necessarily include abiological or metabolic process, and instead may include a standardchemical reaction, such as a hydrolysis reaction, for example, atphysiological pH, or as a result of compartmentalization into a cellularorganelle such as an endosome having a lower pH than cytosolic pH.

It is understood that a cleavable bond can connect two adjacent atomswithin the releasable linker and/or connect other linkers or B, D¹and/or D², as described herein, at either or both ends of the releasablelinker. In the case where a cleavable bond connects two adjacent atomswithin the releasable linker, following breakage of the bond, thereleasable linker is broken into two or more fragments. Alternatively,in the case where a cleavable bond is between the releasable linker andanother moiety, such as another linker, a drug or binding ligand, thereleasable linker becomes separated from the other moiety followingbreaking of the bond.

The lability of the cleavable bond can be adjusted by, for example,substituents at or near the cleavable bond, such as includingalpha-branching adjacent to a cleavable disulfide bond, increasing thehydrophobicity of substituents on silicon in a moiety havingsilicon-oxygen bond that may be hydrolyzed, homologating alkoxy groupsthat form part of a ketal or acetal that may be hydrolyzed, and thelike.

Illustrative releasable linkers described herein include linkers thatinclude hemiacetals and sulfur variations thereof, acetals and sulfurvariations thereof, hemiaminals, aminals, and the like, and can beformed from methylene fragments substituted with at least oneheteroatom, 1-alkoxyalkylene, 1-alkoxycycloalkylene,1-alkoxyalkylenecarbonyl, 1-alkoxycycloalkylenecarbonyl, and the like.Illustrative releasable linkers described herein include linkers thatinclude carbonylarylcarbonyl, carbonyl(carboxyaryl)carbonyl,carbonyl(biscarboxyaryl)carbonyl, haloalkylenecarbonyl, and the like.Illustrative releasable linkers described herein include linkers thatinclude alkylene(dialkylsilyl), alkylene(alkylarylsilyl),alkylene(diarylsilyl), (dialkylsilyl)aryl, (alkylarylsilyl)aryl,(diarylsilyl)aryl, and the like. Illustrative releasable linkersdescribed herein include oxycarbonyloxy, oxycarbonyloxyalkyl,sulfonyloxy, oxysulfonylalkyl, and the like. Illustrative releasablelinkers described herein include linkers that include iminoalkylidenyl,carbonylalkylideniminyl, iminocycloalkylidenyl,carbonylcycloalkylideniminyl, and the like. Illustrative releasablelinkers described herein include linkers that include alkylenethio,alkylenearylthio, and carbonylalkylthio, and the like.

In some embodiments, L² is selected from the group consisting of

wherein

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

X⁶ is C₁-C₆ alkyl or C₆-C₁₀ aryl(C₁-C₆ alkyl), wherein each hydrogenatom in C₁-C₆ alkyl and C₆-C₁₀ aryl(C₁-C₆ alkyl) is independentlyoptionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^(34′),—OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^(34′),—S(O)₂NR³⁴R^(34′), —OS(O)NR³⁴R^(34′), —OS(O)₂NR³⁴R^(34′), —NR³⁴R^(34′),—NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R³⁵, —NR³⁴S(O)R³⁵,—NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^(35′), —NR³⁴S(O)₂NR³⁵R^(35′), —C(O)R³⁴,—C(O)OR³⁴ or —C(O)NR³⁴R^(34′);

each R³², R^(32′), R³³, R^(33′), R³⁴, R^(34′), R³⁵ and R^(35′) areindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, and 5- to 7-membered heteroaryl;

R³⁶ is independently selected from the group consisting of H, D, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³⁷,—OC(O)R³⁷, —OC(O)NR³⁷R^(37′), —OS(O)R³⁷, —OS(O)₂R³⁷, —SR³⁷, —S(O)R³⁷,—S(O)₂R³⁷, —S(O)NR³⁷R^(37′), —S(O)₂NR³⁷R^(37′), —OS(O)NR³⁷R^(37′),—OS(O)₂NR³⁷R^(37′), —NR³⁷R^(37′), —NR³⁷C(O)R³⁸, —NR³⁷C(O)OR³⁸,—NR³⁷C(O)NR³⁸R^(38′), —NR³⁷S(O)R³⁸, —NR³⁷S(O)₂R³⁸, —NR³⁷S(O)NR³⁸R^(38′),—NR³⁷S(O)₂NR³⁸R^(38′), —C(O)R³⁷, —C(O)OR³⁷ or —C(O)NR³⁷R^(37′);

R³⁷, R^(37′), R³⁸ and R^(38′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl; and

* is a covalent bond.

In some embodiments, R³¹ is H. In some embodiments, R³⁶ is H. In someembodiments, X⁶ is C₁-C₆ alkyl. In some embodiments, X⁶ is C₁-C₆ alkyl.C₆-C₁₀ aryl(C₁-C₆ alkyl).

In some embodiments, L² is

wherein

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

X⁶ is C₁-C₆ alkyl or C₆-C₁₀ aryl(C₁-C₆ alkyl), wherein each hydrogenatom in C₁-C₆ alkyl and C₆-C₁₀ aryl(C₁-C₆ alkyl) is independentlyoptionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^(34′),—OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^(34′),—S(O)₂NR³⁴R^(34′), —OS(O)NR³⁴R^(34′) —OS(O)₂NR³⁴R^(34′), —NR³⁴R^(34′),—NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^(35′), —NR³⁴S(O)R³⁵,—NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^(35′), —NR³⁴S(O)₂NR³⁵R^(35′), —C(O)R³⁴,—C(O)OR³⁴ or —C(O)NR³⁴R^(34′);

each R³², R^(32′), R³³, R^(33′), R³⁴, R^(34′), R³⁵ and R^(35′) areindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, and 5- to 7-membered heteroaryl; and

* is a covalent bond.

In some embodiments, R³¹ is H, and X⁶ is C₁-C₆ alkyl. In someembodiments, R³¹ is H, and X⁶ is C₆-C₁₀ aryl(C₁-C₆ alkyl).

In some embodiments, L² is

wherein

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

X⁶ is C₁-C₆ alkyl or C₆-C₁₀ aryl(C₁-C₆ alkyl), wherein each hydrogenatom in C₁-C₆ alkyl and C₆-C₁₀ aryl(C₁-C₆ alkyl) is independentlyoptionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^(34′),—OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^(34′),—S(O)₂NR³⁴R^(34′), —OS(O)NR³⁴R^(34′), —OS(O)₂NR³⁴R^(34′), —NR³⁴R^(34′),—NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R^(35′), —NR³⁴S(O)R³⁵,—NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^(35′), —NR³⁴S(O)₂NR³⁵R^(35′), —C(O)R³⁴,—C(O)OR³⁴ or —C(O)NR³⁴R^(34′);

each R³², R^(32′), R³³, R^(33′), R³⁴, R^(34′), R³⁵ and R^(35′) areindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, and 5- to 7-membered heteroaryl; and

* is a covalent bond.

In some embodiments, R³¹ is H, and X⁶ is C₁-C₆ alkyl. In someembodiments, R³¹ is H, and X⁶ is C₆-C₁₀ aryl(C₁-C₆ alkyl).

In some embodiments, L² is

wherein

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

X⁶ is C₁-C₆ alkyl or C₆-C₁₀ aryl(C₁-C₆ alkyl), wherein each hydrogenatom in C₁-C₆ alkyl and C₆-C₁₀ aryl(C₁-C₆ alkyl) is independentlyoptionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀aryl, 5- to 7-membered heteroaryl, —OR³⁴, —OC(O)R³⁴, —OC(O)NR³⁴R^(34′),—OS(O)R³⁴, —OS(O)₂R³⁴, —SR³⁴, —S(O)R³⁴, —S(O)₂R³⁴, —S(O)NR³⁴R^(34′),—S(O)₂NR³⁴R^(34′), —OS(O)NR³⁴R^(34′), —OS(O)₂NR³⁴R^(34′), —NR³⁴R^(34′),—NR³⁴C(O)R³⁵, —NR³⁴C(O)OR³⁵, —NR³⁴C(O)NR³⁵R³⁵, —NR³⁴S(O)R³⁵,—NR³⁴S(O)₂R³⁵, —NR³⁴S(O)NR³⁵R^(35′), —NR³⁴S(O)₂NR³⁵R^(35′), —C(O)R³⁴,—C(O)OR³⁴ or —C(O)NR³⁴R^(34′);

each R³², R^(32′), R³³, R^(33′), R³⁴, R^(34′), R³⁵ and R^(35′) areindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, and 5- to 7-membered heteroaryl; and

* is a covalent bond.

In some embodiments, R³¹ is H, and X⁶ is C₁-C₆ alkyl. In someembodiments, R³¹ is H, and X⁶ is C₆-C₁₀ aryl(C₁-C₆ alkyl).

In some embodiments, L² is

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

each R³², R^(32′), R³³ and R^(33′) are independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³¹ is H.

In some embodiments, L² is

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

each R³², R^(32′), R³³ and R^(33′) are independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³¹ is H.

In some embodiments, L² is

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

each R³², R^(32′), R³³ and R^(33′) are independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³¹ is H.

In some embodiments, L² is

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

each R³², R^(32′), R³³ and R^(33′) are independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³¹ is H.

In some embodiments, L² is

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

each R³², R^(32′), R³³ and R^(33′) are independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³¹ is H.

In some embodiments, L² is

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

each R³², R^(32′), R³³ and R^(33′) are independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³¹ is H.

In some embodiments, L² is

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

each R³², R^(32′), R³³ and R^(33′) are independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³¹ is H.

In some embodiments, L² is

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′),—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

each R³², R^(32′), R³³ and R^(33′) are independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³¹ is H.

In some embodiments, L² is

R³¹ is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³²,—OC(O)R³², —OC(O)NR³²R^(32′), —OS(O)R³², —OS(O)₂R³², —SR³², —S(O)R³²,—S(O)₂R³², —S(O)NR³²R^(32′), —S(O)₂NR³²R^(32′), —OS(O)NR³²R^(32′)—OS(O)₂NR³²R^(32′), —NR³²R^(32′), —NR³²C(O)R³³, —NR³²C(O)OR³³,—NR³²C(O)NR³³R^(33′), —NR³²S(O)R³³, —NR³²S(O)₂R³³, —NR³²S(O)NR³³R^(33′),—NR³²S(O)₂NR³³R^(33′), —C(O)R³², —C(O)OR³² or —C(O)NR³²R^(32′);

each R³², R^(32′), R³³ and R^(33′) are independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³¹ is H.

In some embodiments, L² is

R³⁶ is independently selected from the group consisting of H, D, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³⁷,—OC(O)R³⁷, —OC(O)NR³⁷R^(37′), —OS(O)R³⁷, —OS(O)₂R³⁷, —SR³⁷, —S(O)R³⁷,—S(O)₂R³⁷, —S(O)NR³⁷R^(37′), —S(O)₂NR³⁷R^(37′), —OS(O)NR³⁷R^(37′),—OS(O)₂NR³⁷R^(37′), —NR³⁷R^(37′), —NR³⁷C(O)R³⁸, —NR³⁷C(O)OR³⁸,—NR³⁷C(O)NR³⁸R^(38′), —NR³⁷S(O)R³⁸, —NR³⁷S(O)₂R³⁸, —NR³⁷S(O)NR³⁸R^(38′),—NR³⁷S(O)₂NR³⁸R^(38′), —C(O)R³⁷, —C(O)OR³⁷ or —C(O)NR³⁷R^(37′);

R³⁷, R^(37′), R³⁸ and R^(38′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³⁶ is H.

In some embodiments, L² is

R³⁶ is independently selected from the group consisting of H, D, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³⁷,—OC(O)R³⁷, —OC(O)NR³⁷R^(37′), —OS(O)R³⁷, —OS(O)₂R³⁷, —SR³⁷, —S(O)R³⁷,—S(O)₂R³⁷, —S(O)NR³⁷R^(37′), —S(O)₂NR³⁷R^(37′), —OS(O)NR³⁷R^(37′),—OS(O)₂NR³⁷R^(37′), —NR³⁷R^(37′), —NR³⁷C(O)R³⁸, —NR³⁷C(O)OR³⁸,—NR³⁷C(O)NR³⁸R^(38′), —NR³⁷S(O)R³⁸, —NR³⁷S(O)₂R³⁸, —NR³⁷S(O)NR³⁸R^(38′),—NR³⁷S(O)₂NR³⁸R^(38′), —C(O)R³⁷, —C(O)OR³⁷ or —C(O)NR³⁷R^(37′);

R³⁷, R^(37′), R³⁸ and R^(38′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³⁶ is H.

In some embodiments, L² is

R³⁶ is independently selected from the group consisting of H, D, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆cycloalkyl is independently optionally substituted by halogen, C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR³⁷,—OC(O)R³⁷, —OC(O)NR³⁷R^(37′), —OS(O)R³⁷, —OS(O)₂R³⁷, —SR³⁷, —S(O)R³⁷,—S(O)₂R³⁷, —S(O)NR³⁷R^(37′), —S(O)₂NR³⁷R^(37′), —OS(O)NR³⁷R^(37′),—OS(O)₂NR³⁷R^(37′), —NR³⁷R^(37′), —NR³⁷C(O)R³⁸, —NR³⁷C(O)OR³⁸,—NR³⁷C(O)NR³⁸R^(38′), —NR³⁷S(O)R³⁸, —NR³⁷S(O)₂R³⁸, —NR³⁷S(O)NR³⁸R^(38′),—NR³⁷S(O)₂NR³⁸R^(38′), —C(O)R³⁷, —C(O)OR³⁷ or —C(O)NR³⁷R^(37′);

R³⁷, R^(37′), R³⁸ and R^(38′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl; and

* is a covalent bond. In some embodiments, R³⁶ is H.

L³ can be present or absent in the conjugates described herein. When L³is present, L³ can be any group covalently attaching portions of thelinker to one another, or to D¹, or to D². It will be understood thatthe structure of L³ is not particularly limited in any way. It will befurther understood that L³ can comprise numerous functionalities wellknown in the art to covalently attach portions of the linker to oneanother, or to D¹, or to D², including but not limited to, alkyl groups,ether groups, amide groups, carboxy groups, sulfonate groups, alkenylgroups, alkynyl groups, cycloalkyl groups, aryl groups,heterocycloalkyl, heteroaryl groups, and the like. In some embodiments,L³ is selected from the group consisting of C₁-C₆ alkyl,—(CR³⁹R^(39′))_(r)C(O)—, —(CR³⁹R^(39′))_(r)OC(O)—,—NR³⁹R^(39′)C(O)(CR³⁹R^(39′))_(r)—, —(CH₂)_(r)NR³⁹—,—(OCR³⁹R^(39′)CR³⁹R^(39′))_(r)C(O)—, and—(OCR³⁹R^(39′)CR³⁹R^(39′)CR³⁹R^(39′))—_(r)C(O)—,

wherein

each R³⁹ and R^(39′) is independently selected from the group consistingof H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR⁴⁰, —OC(O)R⁴⁰, —OC(O)NR⁴⁰R^(40′), —OS(O)R⁴⁰,—OS(O)₂R⁴⁰, —SR⁴⁰, —S(O)R⁴⁰, —S(O)₂R⁴⁰, —S(O)NR⁴⁰R^(40′),—S(O)₂NR⁴⁰R^(40′), —OS(O)NR⁴⁰R^(40′), —OS(O)₂NR⁴⁰R^(40′), —NR⁴⁰R^(40′),—NR⁴⁰C(O)R⁴¹, —NR⁴⁰C(O)OR⁴¹, —NR⁴⁰C(O)NR⁴¹R^(41′)41, —NR⁴⁰S(O)R⁴¹,—NR⁴⁰S(O)₂R⁴¹, —NR⁴⁰S(O)NR⁴¹R^(41′), —NR⁴⁰S(O)₂NR⁴¹R^(41′), —C(O)R⁴⁰,—C(O)OR⁴⁰ and —C(O)NR⁴⁰R^(40′);

R⁴⁰, R^(40′), R⁴¹ and R^(41′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5-to 7-membered heteroaryl; and

r in each instance is 1, 2, 3, 4, or 5. In some embodiments of theconjugates described herein, L³ is present. In some embodiments of theconjugates described herein, L³ is absent. In some embodiments, z2 is 0.In some embodiments, z2 is 1. In some embodiments, z2 is 2. In someembodiments, z6 is 0. In some embodiments, z6 is 1. In some embodiments,z6 is 2. In some embodiments, r is 5. In some embodiments, r is 4. Insome embodiments, r is 3. In some embodiments, r is 5, each R³⁹ is H,and each R^(39′) is H. In some embodiments, r is 4, each R³⁹ is H, andeach R^(39′) is H. In some embodiments, r is 3, each R³⁹ is H, and eachR^(39′) is H.

In some embodiments, L³ is —(CR³⁹R^(39′))_(r)C(O)—. In some embodiments,L³ is —(CR³⁹R^(39′))_(r)C(O)—, r is 5, each R³⁹ is H, and each R^(39′)is H. In some embodiments, L³ is —(CR³⁹R^(39′))_(r)C(O)—, r is 4, eachR³⁹ is H, and each R^(39′) is H. In some embodiments, L³ is—(CR³⁹R^(39′))_(r)C(O)—, r is 3, each R³⁹ is H, and each R^(39′) is H.

In some embodiments, L³ is —(CR³⁹R^(39′))_(r)OC(O)—, r is 5, each R³⁹ isH, and each R^(39′) is H. In some embodiments, L³ is—(CR³⁹R^(39′))_(r)OC(O)—, r is 4, each R³⁹ is H, and each R^(39′) is H.In some embodiments, L³ is —(CR³⁹R^(39′))_(r)OC(O)—, r is 3, each R³⁹ isH, and each R^(39′) is H.

In some embodiments, L³ is —NR³⁹R^(39′)C(O)(CR³⁹R^(39′))_(r)—, r is 5,each R³⁹ is H, and each R^(39′) is H. In some embodiments, L³ is—NR³⁹R^(39′)C(O)(CR³⁹R^(39′))_(r)—, r is 4, each R³⁹ is H, and eachR^(39′) is H. In some embodiments, L³ is—NR³⁹R^(39′)C(O)(CR³⁹R^(39′))_(r)—, r is 3, each R³⁹ is H, and eachR^(39′) is H.

In some embodiments, L³ is —(CH₂)_(r)NR³⁹—, r is 5 and R³⁹ is H. In someembodiments, L³ is —(CH₂)_(r)NR³⁹—, r is 4 and R³⁹ is H. In someembodiments, L³ is —(CH₂)_(r)NR³⁹—, r is 3 and R³⁹ is H. In someembodiments, L³ is —(CH₂)_(r)NR³⁹—, r is 2 and R³⁹ is H.

In some embodiments, L³ is —(OCR³⁹R^(39′)CR³⁹R^(39′))_(r)C(O)—, r is 5,each R³⁹ is H, and each R^(39′) is H. In some embodiments, L³ is—(OCR³⁹R^(39′)CR³⁹R^(39′))_(r)C(O)—, r is 4, each R³⁹ is H, and eachR^(39′) is H. In some embodiments, L³ is—(OCR³⁹R^(39′)CR³⁹R^(39′))_(r)C(O)—, r is 3, each R³⁹ is H, and eachR^(39′) is H.

L⁴ can be present or absent in the conjugates described herein. When L⁴is present, L⁴ can be any group covalently attaching portions of thelinker to one another, or to D¹, or to D². It will be understood thatthe structure of L⁴ is not particularly limited in any way. It will befurther understood that L⁴ can comprise numerous functionalities wellknown in the art to covalently attach portions of the linker to oneanother, or to D¹, or to D², including but not limited to, alkyl groups,ether groups, amide groups, carboxy groups, sulfonate groups, alkenylgroups, alkynyl groups, cycloalkyl groups, aryl groups,heterocycloalkyl, heteroaryl groups, and the like. In some embodiments,L⁴ is selected from the group consisting of —C(O)(CR⁴⁴R^(44′))_(t)—,—NR⁴²CR⁴³R^(43′) CR⁴³R^(43′)(OCR⁴⁴R^(44′)CR⁴⁴R^(44′))_(t)—,—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(OCR⁴⁴R^(44′) CR⁴⁴R^(44′))_(t)—,—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(OCR⁴⁴R^(44′) CR⁴⁴R^(44′))_(t)C(O)—,—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(CR⁴⁴═CR^(44′))_(t)—, and —NR⁴²C₆-C₁₀aryl(C₁-C₆ alkyl)OC(O)—;

wherein

R⁴² is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, wherein each hydrogen atomin C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl isindependently optionally substituted by halogen, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR⁴⁵,—OC(O)R⁴⁵, —OC(O)NR⁴⁵R^(45′), —OS(O)R⁴⁵, —OS(O)₂R⁴⁵, —SR⁴⁵, —S(O)R⁴⁵,—S(O)₂R⁴⁵, —S(O)NR⁴⁵R^(45′), —S(O)₂NR⁴⁵R^(45′), —OS(O)NR⁴⁵R⁴⁵,—OS(O)₂NR⁴⁵R^(45′), —NR⁴⁵R^(45′), —NR⁴⁵C(O)R⁴⁶, —NR⁴⁵C(O)OR⁴⁶,—NR⁴⁵C(O)NR⁴⁶R^(46′), —NR⁴⁵S(O)R⁴⁶, —NR⁴⁵S(O)₂R⁴⁶, —NR⁴⁵S(O)NR⁴⁶R^(46′),—NR⁴⁵S(O)₂NR⁴⁶R^(46′), —C(O)R⁴⁵, —C(O)OR⁴⁵ or —C(O)NR⁴⁵R^(45′),

each R⁴³, R^(43′), R⁴⁴ and R⁴⁴ is independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆cycloalkyl, wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl and C₃-C₆ cycloalkyl is independently optionallysubstituted by halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR⁴⁷, —OC(O)R⁴⁷, —OC(O)NR⁴⁷R^(47′), —OS(O)R⁴⁷,—OS(O)₂R⁴⁷, —SR⁴⁷, —S(O)R⁴⁷, —S(O)₂R⁴⁷, —S(O)NR⁴⁷R^(47′),—S(O)₂NR⁴⁷R^(47′), —OS(O)NR⁴⁷R^(47′), —OS(O)₂NR⁴⁷R^(47′), —NR⁴⁷R^(47′),—NR⁴⁷C(O)R⁴⁸, —NR⁴⁷C(O)OR⁴⁸, —NR⁴⁷C(O)NR⁴⁸R^(48′), —NR⁴⁷S(O)R⁴⁸,—NR⁴⁷S(O)₂R⁴⁸, —NR⁴⁷S(O)NR⁴⁸R^(48′), —NR⁴⁷S(O)₂NR⁴⁸R^(48′), —C(O)R⁴⁷,—C(O)OR⁴⁷ or —C(O)NR⁴⁷R^(47′);

R⁴⁵, R^(45′), R⁴⁶, R^(46′), R⁴⁷, R^(47′), R⁴⁸ and R^(48′) are eachindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl;

t is in each instance 1, 2, 3, 4, or 5; and

* is a covalent bond.

In some embodiments of the conjugates described herein, L⁴ is present.In some embodiments of the conjugates described herein, L⁴ is absent. Insome embodiments, z5 is 0. In some embodiments, z5 is 1. In someembodiments, z5 is 2. In some embodiments, z7 is 0. In some embodiments,z7 is 1. In some embodiments, z7 is 2. In some embodiments, z9 is 0. Insome embodiments, z9 is 1. In some embodiments, z9 is 2. In someembodiments, z7 is 0 and z9 is 0. In some embodiments, z7 is 0 and z9is 1. In some embodiments, z7 is 1 and z9 is 1. In some embodiments, z7is 1 and z9 is 0.

In some embodiments, L⁴ is —NR⁴²C₆-C₁₀ aryl(C₁-C₆ alkyl)OC(O)—, whereinR⁴² is H. In some embodiments, z5 is 1, and L⁴ is —NR⁴²C₆-C₁₀ aryl(C₁-C₆alkyl)OC(O)—, wherein R⁴² is H. In some embodiments, z7 is 1, and L⁴ is—NR⁴²C₆-C₁₀ aryl(C₁-C₆ alkyl)OC(O)—, wherein R⁴² is H. In someembodiments, z9 is 1, and L⁴ is —NR⁴²C₆-C₁₀ aryl(C₁-C₆ alkyl)OC(O)—,wherein R⁴² is H. In some embodiments, L⁴ is—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(OCR⁴⁴R^(44′)CR⁴⁴R^(44′))_(t)C(O)— whereineach R⁴², R⁴³, R^(43′), R⁴⁴ and R^(44′) is H, and t is 4. In someembodiments, L⁴ is—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(OCR⁴⁴R^(44′)CR⁴⁴R^(44′))_(t)C(O)— or—NR⁴²C₆-C₁₀ aryl(C₁-C₆ alkyl)OC(O)—, wherein each R⁴², R⁴³, R^(43′), R⁴⁴and R^(44′) is H, z7 is 1, z9 is 1, and t is 4.

In some embodiments, -L³-L⁴- is —(CH₂)_(r)NR³⁹C(O)(CR⁴⁴R^(44′))_(t)—,wherein r is 2, t is 2, R³⁹ is H, each R⁴⁴ is H, and each R^(44′) is H.In some embodiments, -L³-L⁴-(AA)₂ is—(CR³⁹R^(39′))_(r)C(O)—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(OCR⁴⁴R^(44′)CR⁴⁴R^(44′))_(t)C(O)-Val-Ala-,-L³-L⁴-(AA)₂-L⁴ is—(CR³⁹R^(39′))_(r)C(O)—NR⁴²CR⁴³R^(43′)CR⁴³R^(43′)(OCR⁴⁴R^(44′)CR⁴⁴R^(44′))_(t)C(O)-Val-Ala-NR⁴²C₆-C₁₀aryl(C₁-C₆ alkyl)OC(O)—, wherein each R³⁹, R^(39′), R⁴², R⁴³, R^(43′),R⁴⁴ and R^(44′) is H, r is 2 and t is 4.

L⁵ can be present or absent in the conjugates described herein. When L⁵is present, L⁵ can be any group covalently attaching D¹ to D². It willbe understood that the structure of L⁵ is not particularly limited inany way. It will be further understood that L⁵ can comprise numerousfunctionalities well known in the art to covalently attach D¹ to D²,including but not limited to, alkyl groups, ether groups, amide groups,carboxy groups, sulfonate groups, alkenyl groups, alkynyl groups,cycloalkyl groups, aryl groups, heterocycloalkyl, heteroaryl groups, andthe like. In some embodiments, L⁵ is selected from the group consistingof C₁-C₁₀ alkyl, —(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—,—CH₂CH₂(OCR⁴⁹R^(49′) CR⁴⁹R^(49′))_(u)—,—CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— and—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R⁴⁹CR⁴⁹R^(49′))_(u)C(O)—, wherein

each R⁴⁹ and R^(49′) is independently selected from the group consistingof H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl,wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyland C₃-C₆ cycloalkyl is independently optionally substituted by halogen,C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl,—OR⁵⁰, —OC(O)R⁵⁰, —OC(O)NR⁵⁰R^(50′), —OS(O)R⁵⁰, —OS(O)₂R⁵⁰, —SR⁵⁰,—S(O)R⁵⁰, —S(O)₂R⁵⁰, —S(O)NR⁵⁰R^(50′), —S(O)₂NR⁵⁰R^(50′),—OS(O)NR⁵⁰R^(50′), —OS(O)₂NR⁵⁰R^(50′), —NR⁵⁰R^(50′), —NR⁵⁰C(O)R⁵¹,—NR⁵⁰C(O)OR⁵¹, —NR⁵⁰C(O)NR⁵¹R^(51′), —NR⁵⁰S(O)R⁵¹, —NR⁵⁰S(O)₂R⁵¹,—NR⁵⁰S(O)NR⁵¹R^(51′), —NR⁵⁰S(O)₂NR⁵¹R^(51′), —C(O)R⁵⁰, —C(O)OR⁵⁰ or—C(O)NR⁵⁰R^(50′);

R⁵⁰, R^(50′), R⁵¹ and R^(51′) are each independently selected from thegroup consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl;

u is in each instance 0, 1, 2, 3, 4 or 5; and

* is a covalent bond.

In some embodiments of the conjugates described herein, L⁵ is present.In some embodiments of the conjugates described herein, L⁵ is absent. Insome embodiments, L⁵ is C₁-C₆ alkyl. In some embodiments, L⁵ is—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 3.In some embodiments, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ andR^(49′) is H, and u is 4. In some embodiments, L⁵ is—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 5.

In some embodiments, the linker is of the formula-(AA)_(z1)-L²-(L³)_(z2)-(AA)_(z3)-(L¹)_(z4)-(L⁴)_(z5)-, wherein AA, L¹,L², L³, L⁴, z1, z2, z3, z4 and z5 are defined as described herein. Insome embodiments, the linker is of the formula-L¹-AA-L¹-AA-L¹-L²-(L³)_(z6)-(L⁴)_(z7)-(AA)_(z8)-(L⁴)_(z9)-, wherein AA,L¹, L², L³, L⁴, z6, z7, z8 and z9 are defined as described herein. Insome embodiments, the linker is of the formula -(AA)_(z10)-L²-, whereinAA, L² and z10 are defined as described herein. In some embodiments, thelinker is of the formula -(AA)_(z11)-L²-, wherein AA, L², and z11 aredefined as described herein. In some embodiments, the linker is of theformula -L²-(AA)_(z12)-, wherein AA, L², and z12 are defined asdescribed herein. In some embodiments, the linker is of the formula-(AA)₄-L²-, wherein AA and L² are defined as described herein. In someembodiments, the linker is of the formula -(AA)₄-L²-, wherein thesequence of -(AA)₄- is -Asp-Arg-Asp-Asp-, and L² is defined as describedherein. In some embodiments, the linker is of the formula-(AA)₄-L²-L³-AA-L¹-L⁴-, wherein the sequence of -(AA)₄- is-Asp-Arg-Asp-Asp-, and AA, L¹, L², L³ and L⁴ are defined as describedherein. In some embodiments, the linker is of the formula-(AA)₄-L²-L³-(AA)₂-, wherein AA, L¹, L² and L³ are defined as describedherein. In some embodiments, the linker is of the formula-(AA)₄-L²-L³-(AA)₂-, wherein the sequence of -(AA)₄- is-Asp-Arg-Asp-Asp-, the sequence of -(AA)₂- is Val-Ala, and L¹, L² and L³are defined as described herein. In some embodiments, the linker is ofthe formula -(AA)₄-L²-L³-(AA)₂-, wherein the sequence of -(AA)₄- is-Asp-Arg-Asp-Asp-, the sequence of -(AA)₂- is Val-CIT, and L¹, L² and L³are defined as described herein. In some embodiments, the linker is ofthe formula -L¹-AA-L¹-AA-L¹-L²-, wherein AA, L¹ and L² are defined asdescribed herein. In some embodiments, the linker is of the formula-L1-AA-L1-AA-L1-L2-L3-(AA)₂-L4-, wherein AA, L¹, L², L³ and L⁴ aredefined as described herein. In some embodiments, the linker is of theformula -L¹-AA-L¹-AA-L¹-L²-L³-L⁴-(AA)₂-L⁴-, wherein AA, L¹, L², L³ andL⁴ are defined as described herein. In some embodiments, the linker isof the formula -L¹-AA-L¹-AA-L¹-L²-L³-L⁴-, AA, L¹, L², L³ and L⁴ aredefined as described herein. In some embodiments, the linker is of theformula -L¹-AA-L¹-AA-L¹-L²-L³-(AA)₂-, wherein AA, L¹, L² and L³ aredefined as described herein. -L¹-AA-L¹-AA-L¹-L²-L³-, wherein AA, L¹, L²and L³ are defined as described herein.

In some embodiments, the linker is of the formula

wherein * is a bond.

In some embodiments, the linker is of the formula

wherein * is a bond.

In some embodiments, the linker is of the formula

wherein * is a bond.

In some embodiments, the linker is of the formula

wherein * is a bond.

In some embodiments, the linker is of the formula

wherein * is a bond.

In some embodiments, the linker is of the formula

wherein * is a bond.

In some embodiments, the linker is of the formula

wherein * is a bond.

In some embodiments, the linker is of the formula

wherein * is a bond.

In some embodiments, the linker is of the formula

wherein * is a bond.

In the conjugates described herein, Drug describes one or two drugsselected D¹ and/or D², covalently attached to one or more linkerportions of the conjugate. In some embodiments, both D¹ and D² arepresent. In some embodiments, D comprises the structure -D¹-L⁵-D². Insome embodiments, Drug comprises the structure -D¹-L⁵-D¹-.

Certain of the drugs D¹ and D² described herein comprisepyrrolobenzodiazepine (PBD) prodrugs. It will be understood that suchPBD prodrugs undergo conversion to a therapeutically active PBD compoundthrough processes in the body after delivery of a conjugate as describedherein. In some embodiments, at least one of the drugs incorporated intoconjugates described herein is a PBD prodrug as described herein.

D¹ can be described as a PBD prodrug of the formula III

wherein

R^(1a), R^(2a), R^(3a) and R^(4a) are each independently selected fromthe group consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(11a), —C(O)OR^(11a) and—C(O)NR^(11a)R^(11a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(11a), —OC(O)R^(11a),—OC(O)NR^(11a)R^(11a′), —OS(O)R^(11a), —OS(O)₂R^(11a), —SR^(11a),—S(O)R^(11a), —S(O)₂R^(11a), —S(O)NR^(11a)R^(11a′),—S(O)₂NR^(11a)R^(11a′), —OS(O)NR^(11a)R^(11a′), —OS(O)₂NR^(11a)R^(11a′),—NR^(11a)R^(11a′), —NR^(11a)C(O)R^(12a), —NR^(11a)C(O)OR^(12a),—NR^(11a)C(O)NR^(12a)R^(12a′), —NR^(11a)S(O)R^(12a),—NR^(11a)S(O)₂R^(12a), —NR^(11a)S(O)NR^(2a)R^(12a′),—NR^(11a)S(O)₂NR^(12a)R^(12a′), —C(O)R^(11a), —C(O)OR^(11a) or—C(O)NR^(11a)R^(11a′); or R^(1a) is a bond; or R^(4a) is a bond;

R^(5a), R^(6a) and R^(7a) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(13a), —C(O)OR^(13a) and—C(O)NR^(13a)R^(13a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isoptionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR^(14a), —OC(O)R^(14a), —OC(O)NR^(14a)R^(14a′),—OS(O)R^(14a), —OS(O)₂R^(14a), —SR^(14a), —S(O)R^(14a), —S(O)₂R^(14a),—S(O)NR^(14a)R^(14a′), —S(O)₂NR^(14a)R^(14a′), —OS(O)NR^(14a)R^(14a′),—OS(O)₂NR^(14a)R^(14a′), —NR^(14a)R^(14a′), —NR^(14a)C(O)R^(15a),—NR^(14a)C(O)OR^(15a), —NR^(14a)C(O)NR^(15a)R^(15a′),—NR^(14a)S(O)R^(15a), —NR^(14a)S(O)₂R^(15a),—NR^(14a)S(O)NR^(15a)R^(15a′), —NR^(14a)S(O)₂NR^(15a)R^(15a′),—C(O)R^(14a), —C(O)OR^(14a) or —C(O)NR^(14a)R^(14a′); wherein R^(6a) andR^(7a) taken together with the atoms to which they are attachedoptionally combine to form a 3- to 7-membered heterocycloalkyl, orR^(5a) and R^(6a) taken together with the atoms to which they areattached optionally combine to form a 3- to 7-membered heterocycloalkylor 5- to 7-membered heteroaryl, wherein each hydrogen atom in 3- to7-membered heterocycloalkyl or 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(16a), —OC(O)R^(16a),—OC(O)NR^(16a)R^(16a′), —OS(O)R^(16a), —OS(O)₂R^(16a), —SR^(16a),—S(O)R^(16a), —S(O)₂R^(16a), —S(O)NR^(16a)R^(16a′),—S(O)₂NR^(16a)R^(16a′), —OS(O)NR^(16a)R^(16a′), —OS(O)₂NR^(16a)R^(16a′),—NR^(16a)R^(16a′), —NR^(16a)C(O)R^(17a), —NR^(16a)C(O)CH₂CH₂ ⁻,—NR^(16a)C(O)OR^(17a), —NR^(16a)C(O)NR^(17a)R^(17a′),—NR^(16a)S(O)R^(17a), —NR^(16a)S(O)₂R^(17a),—NR^(16a)S(O)NR^(17a)R^(17a′), —NR^(16a)S(O)₂NR^(17a)R^(17a′),—C(O)R^(16a), —C(O)OR^(16a) or —C(O)NR^(16a)R^(16a′), and wherein onehydrogen atom in 5- to 7-membered heteroaryl is optionally a bond, orR^(5a) is a bond;

R^(8a) and R^(9a) are each independently selected from the groupconsisting of H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OR^(18a), —OC(O)R^(18a),—OC(O)NR^(18a)R^(18a′), —OS(O)R^(18a), —OS(O)₂R^(18a), —SR^(18a),—S(O)R^(18a), —S(O)₂R^(18a), —S(O)NR^(18a)R^(18a′),—S(O)₂NR^(18a)R^(18a′), —OS(O)NR^(18a)R^(18a′), —OS(O)₂NR^(18a)R^(11a′),—NR^(18a)R^(18a′), —NR^(18a)C(O)R^(19a), —NR^(18a)C(O)OR^(19a),—NR^(18a)C(O)NR^(19a)R^(19a′), —NR^(18a)S(O)R^(19a),—NR^(18a)S(O)₂R^(19a), —NR^(18a)S(O)NR^(19a)R^(19a′),—NR^(18a)S(O)₂NR^(19a)R^(19a′), —C(O)R^(18a), —C(O)OR^(18a) and—C(O)NR^(18a)R^(18a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(20a), —OC(O)R^(20a),—OC(O)NR^(20a)R^(20a′), —OS(O)R^(20a), —OS(O)₂R^(20a), —SR^(20a),—S(O)R^(20a), —S(O)₂R^(20a), —S(O)NR^(20a)R^(20a′),—S(O)₂NR^(20a)R^(20a′), —OS(O)NR^(20a)R^(20a′), —OS(O)₂NR^(20a)R^(20a′),—NR^(20a)R^(20a′), —NR^(20a)C(O)R^(21a), —NR^(20a)C(O)OR^(21a),—NR^(20a)C(O)NR^(2a)R^(21a′), —NR^(20a)S(O)R^(21a),—NR^(20a)S(O)₂R^(21a), —NR^(20a)S(O)NR^(21a)R^(21a′),—NR^(20a)S(O)₂NR^(21a)R^(21a′), —C(O)R^(20a), —C(O)OR^(20a) or—C(O)NR^(20a)R^(20a′);

R^(10a) is selected from the group consisting of H, D, C₁-C₆ alkyl,C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(22a),—OC(O)R^(22a), —OC(O)NR^(22a)R^(22a′), —OS(O)R^(22a), —OS(O)₂R^(22a),—SR^(22a), —S(O)R^(22a), —S(O)₂R^(22a), —S(O)NR^(22a)R^(22a′),—S(O)₂NR^(22a)R^(22a′), —OS(O)NR^(22a)R^(22a′), —OS(O)₂NR^(22a)R^(22a′),—NR^(22a)R^(22a′), —NR^(22a)C(O)R^(23a), —NR^(22a)C(O)OR^(23a),—NR^(22a)C(O)NR^(23a)R^(23a′), —NR^(22a)S(O)R^(23a),—NR^(22a)S(O)₂R^(23a), —NR^(22a)S(O)NR^(23a)R^(23a′),—NR^(22a)S(O)₂NR^(23a)R^(23a), —C(O)R^(22a), —C(O)OR^(23a) and—C(O)NR^(22a)R^(22a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(24a), —OC(O)R^(24a),—OC(O)NR^(24a)R^(24a′), —OS(O)R^(24a), —OS(O)₂R^(24a), —SR^(24a),—S(O)R^(24a), —S(O)₂R^(24a), —S(O)NR^(24a)R^(24a′),—S(O)₂NR^(24a)R^(24a′), —OS(O)NR^(24a)R^(24a′), —OS(O)₂NR^(24a)R^(24a′),—NR^(24a)R^(24a′), —NR^(24a)C(O)R^(25a), —NR^(24a)C(O)OR^(25a),—NR^(24a)C(O)NR^(25a)R^(25a′), —NR^(24a)S(O)R^(25a),—NR^(24a)S(O)₂R^(25a), —NR^(24a)S(O)NR^(25a)R^(25a′),—NR^(24a)S(O)₂NR^(25a)R^(25a′), —C(O)R^(24a), —C(O)OR^(24a) or—C(O)NR^(24a)R^(24a′); and

each R^(11a), R^(11a′), R^(12a), R^(12a′), R^(13a), R^(13a′), R^(14a),R^(14a′), R^(15a), R^(15a′), R^(16a), R^(16a′), R^(17a), R^(17a′),R^(18a), R^(18a′), R^(19a), R^(19a′), R^(20a), R^(20a′), R^(21a),R^(21a′), R^(22a), R^(22a′), R^(23a), R^(23a′), R^(24a), R^(24a′),R^(25a) and R^(25a′) is independently selected from the group consistingof H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₁₃ cycloalkyl,3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and 5- to 7-memberedheteroaryl;

provided that at least two of R^(1a), R^(4a) and R^(5a) are a bond, orwhen R^(5a) and R^(6a) taken together with the atoms to which they areattached optionally combine to form a 3- to 7-membered heterocycloalkylor 5- to 7-membered heteroaryl, one hydrogen atom in 5- to 7-memberedheteroaryl is a bond and one of R^(1a) or R^(4a) is a bond.

In some embodiments, R^(1a) is a bond, and R^(5a) is a bond. In someembodiments, R^(1a) is a bond, and R^(4a) is a bond. In someembodiments, R^(1a) is a bond, and R^(2a) is C₁-C₆ alkyl. In someembodiments, R^(1a) is a bond, R^(3a) is H, and R^(4a) is H. In someembodiments, R^(1a) is a bond, and R^(2a) is C₁-C₆ alkyl. In someembodiments, R^(1a) is a bond, R^(2a) is C₁-C₆ alkyl, R^(3a) is H, andR^(4a) is H. In some embodiments, R^(1a) is a bond, R^(5a) is a bond,and R^(6a) and R^(7a) taken together with the atoms to which they areattached optionally combine to form a 3- to 7-membered heterocycloalkyl.In some embodiments, R^(1a) is a bond, and R^(5a) and R^(6a) takentogether with the atoms to which they are attached optionally combine toform a 3- to 7-membered heterocycloalkyl or 5- to 7-membered heteroaryl,wherein one hydrogen atom in 5- to 7-membered heteroaryl is a bond.

In some embodiments, R^(5a), R^(6a) and R^(7a) are each independentlyselected from the group consisting of H, C₁-C₆ alkyl, —C(O)R^(13a),—C(O)OR^(13a), wherein each hydrogen atom in C₁-C₆ alkyl is optionallysubstituted by —OC(O)R^(14a); wherein R^(6a) and R^(7a) taken togetherwith the atoms to which they are attached optionally combine to form a3- to 7-membered heterocycloalkyl, or R^(5a) and R^(6a) taken togetherwith the atoms to which they are attached optionally combine to form a3- to 7-membered heterocycloalkyl or 5- to 7-membered heteroaryl,provided that at least two of R^(1a), R^(4a) and R^(5a) are a bond, orwhen R^(5a) and R^(6a) taken together with the atoms to which they areattached optionally combine to form a 3- to 7-membered heterocycloalkylor 5- to 7-membered heteroaryl, one hydrogen atom in 5- to 7-memberedheteroaryl is a bond and one of R^(1a) or R^(4a) is a bond; and eachR^(13a) and R^(14a) is independently H or C₁-C₇ alkyl.

In some embodiments, D¹ is a PBD prodrug of the formula IIIa

wherein

R^(2a), R^(3a) and R^(4a) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(11a), —C(O)OR^(11a), and—C(O)NR^(11a)R^(11a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(11a), —OC(O)R^(11a),—OC(O)NR^(11a)R^(11a′), —OS(O)R^(11a), —OS(O)₂R^(11a), —SR^(11a),—S(O)R^(11a), —S(O)₂R^(11a), —S(O)NR^(11a)R^(11a′),—S(O)₂NR^(11a)R^(11a′), —OS(O)NR^(11a)R^(11a′), —OS(O)₂NR^(11a)R^(11a′),—NR^(11a)R^(11a′), —NR^(11a)C(O)R^(12a), —NR^(11a)C(O)OR^(12a),—NR^(11a)C(O)NR^(12a)R^(12a′), —NR^(11a)S(O)R^(12a),—NR^(11a)S(O)₂R^(12a), —NR^(11a)S(O)NR^(12a)R^(12a′),—NR^(11a)S(O)₂NR^(12a)R^(12a′), —C(O)R^(11a), —C(O)OR^(11a) or—C(O)NR^(11a)R^(11a′);

R^(8a) and R^(9a) are each independently selected from the groupconsisting of H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OR^(18a), —OC(O)R^(18a),—OC(O)NR^(18a)R^(18a′), —OS(O)R^(18a), —OS(O)₂R^(18a), —SR^(18a),—S(O)R^(18a), —S(O)₂R^(18a), —S(O)NR^(18a)R^(18a),—S(O)₂NR^(18a)R^(18a′), —OS(O)NR^(18a)R^(8a′), —OS(O)₂NR^(18a)R^(18a′),—NR^(18a)R^(18a′), —NR^(18a)C(O)R^(19a), —NR^(18a)C(O)OR^(19a),—NR^(18a)C(O)NR^(19a)R^(19a′), —NR^(18a)S(O)R^(19a),—NR^(18a)S(O)₂R^(19a), —NR^(18a)S(O)NR^(19a)R^(19a′),—NR^(18a)S(O)₂NR^(19a)R^(19a′), —C(O)R^(18a), —C(O)OR^(18a) and—C(O)NR^(18a)R^(18a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(20a), —OC(O)R^(20a),—OC(O)NR^(20a)R^(20a′), —OS(O)R^(20a), —OS(O)₂R^(20a), —SR^(20a),—S(O)R^(20a), —S(O)₂R^(20a), —S(O)NR^(20a)R^(20a′),—S(O)₂NR^(20a)R^(20a′), —OS(O)NR^(20a)R^(20a′), —OS(O)₂NR^(20a)R^(20a′),—NR^(20a)R^(20a′), —NR^(20a)C(O)R^(21a), —NR^(20a)C(O)OR^(21a),—NR^(20a)C(O)NR^(21a)R^(21a′), —NR^(20a)S(O)R^(21a),—NR^(20a)S(O)₂R^(21a), —NR^(20a)S(O)NR^(21a)R^(21a′),—NR^(20a)S(O)₂NR^(21a)R^(21a′), —C(O)R^(20a), —C(O)OR^(20a) or—C(O)NR^(20a)R^(2a′);

each R^(11a), R^(11a′), R^(12a), R^(12a′), R^(18a), R^(18a′), R^(19a),R^(19a′), R^(20a), R^(20a′), R^(21a) and R^(21a′) is independentlyselected from the group consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl,C₂-C₇ alkynyl, C₃-C₁₃ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, and 5- to 7-membered heteroaryl; and

* is a bond. In some embodiments, R^(2a), R^(3a) and R^(4a) are eachindependently H or C₁-C₆ alkyl; R^(8a) and R^(9a) are each H, and * is abond.

In some embodiments, D¹ is a PBD prodrug of the formula IIIb

wherein

R^(2a) and R^(3a) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(11a), —C(O)OR^(11a), and—C(O)NR^(11a)R^(11a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(11a), —OC(O)R^(11a),—OC(O)NR^(11a)R^(11a′), —OS(O)R^(11a), —OS(O)₂R^(11a), —SR^(11a),—S(O)R^(11a), —S(O)₂R^(11a), —S(O)NR^(11a)R^(11a′),—S(O)₂NR^(11a)R^(11a′), —OS(O)NR^(11a)R^(11a′), —OS(O)₂NR^(11a)R^(11a′),—NR^(11a)R^(11a′), —NR^(11a)C(O)R^(12a), —NR^(11a)C(O)OR^(12a),—NR^(11a)C(O)NR^(12a)R^(12a′), —NR^(11a)S(O)R^(12a),—NR^(11a)S(O)₂R^(12a), —NR^(11a)S(O)NR^(12a)R^(12a′),—NR^(11a)S(O)₂NR^(12a)R^(12a′), —C(O)R^(11a), —C(O)OR^(11a) or—C(O)NR^(11a)R^(11a′);

R^(5a) is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl,—C(O)R^(13a), —C(O)OR^(13a) and —C(O)NR^(13a)R^(13a′), wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl is optionally substituted by C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(14a),—OC(O)R^(14a), —OC(O)NR^(14a)R^(14a′), —OS(O)R^(14a), —OS(O)₂R^(14a),—SR^(14a), —S(O)R^(14a), —S(O)₂R^(14a), —S(O)NR^(14a)R^(14a′),—S(O)₂NR^(14a)R^(14a′), —OS(O)NR^(14a)R^(14a′), —OS(O)₂NR^(14a)R^(14a′),—NR^(14a)R^(14a′), —NR^(14a)C(O)R^(15a), —NR^(14a)C(O)OR^(15a),—NR^(14a)C(O)NR^(15a)R^(15a′), —NR^(14a)S(O)R^(15a),—NR^(14a)S(O)₂R^(15a), —NR^(14a)S(O)NR^(15a)R^(15a′),—NR^(14a)S(O)₂NR^(15a)R^(15a′), —C(O)R^(14a), —C(O)OR^(14a) or—C(O)NR^(14a)R^(14a′);

R^(8a) and R^(9a) are each independently selected from the groupconsisting of H, D, halogen, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OR^(18a), —OC(O)R^(18a),—OC(O)NR^(18a)R^(18a′), —OS(O)R^(18a), —OS(O)₂R^(18a), —SR^(18a),—S(O)R^(18a), —S(O)₂R^(18a), —S(O)NR^(18a)R^(18a′),—S(O)₂NR^(18a)R^(18a′), —OS(O)NR^(18a)R^(18a′), —OS(O)₂NR^(18a)R^(18a′),—NR^(18a)R^(18a′), —NR^(18a)C(O)R^(19a), —NR^(18a)C(O)OR^(19a),—NR^(18a)C(O)NR^(19a)R^(19a′), —NR^(18a)S(O)R^(19a),—NR^(18a)S(O)₂R^(19a), —NR^(18a)S(O)NR^(19a)R^(19a′),—NR^(18a)S(O)₂NR^(19a)R^(19a′), —C(O)R^(18a), —C(O)OR^(18a) and—C(O)NR^(18a)R^(18a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(20a), —OC(O)R^(20a),—OC(O)NR^(20a)R^(20a′), —OS(O)R^(20a), —OS(O)₂R^(20a), —SR^(20a),—S(O)R^(20a), —S(O)₂R^(20a), —S(O)NR^(20a)R^(20a′),—S(O)₂NR^(20a)R^(20a′), —OS(O)NR^(20a)R^(20a′), —OS(O)₂NR^(20a)R^(20a′),—NR^(20a)R^(20a′), —NR^(20a)C(O)R^(21a), —NR^(20a)C(O)OR^(21a),—NR^(20a)C(O)NR^(21a)R^(21a′), —NR^(20a)S(O)R^(21a),—NR^(20a)S(O)₂R^(21a), —NR^(20a)S(O)NR^(21a)R^(21a′),—NR^(20a)S(O)₂NR^(21a)R^(21a′), —C(O)R^(20a), —C(O)OR^(20a) or—C(O)NR^(20a)R^(20a′);

each R^(11a), R^(11a′), R^(12a), R^(12a′), R^(13a), R^(13a′), R^(14a),R^(14a′), R^(15a), R^(15a′), R^(18a), R^(18a′), R^(19a), R^(19a′),R^(20a), R^(20a′), R^(21a) and R^(21a′) is independently selected fromthe group consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₁₃ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and5- to 7-membered heteroaryl; and * is a bond. In some embodiments,R^(2a) and R^(3a) are each independently H or C₁-C₆ alkyl; R^(5a) isselected from the group consisting of H, C₁-C₆ alkyl, —C(O)R^(13a), and—C(O)OR^(13a), wherein each hydrogen atom in C₁-C₆ alkyl is optionallysubstituted by C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR^(14a), —OC(O)R^(14a), R^(13a) and R^(14a) areeach independently selected from the group consisting of H, D, C₁-C₇alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₁₃ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, and 5- to 7-membered heteroaryl; R^(8a)and R^(9a) are each H, and * is a bond.

In some embodiments, D¹ is a PBD prodrug of the formula IIIc

wherein

R^(2a), R^(3a) and R^(4a) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(11a), —C(O)OR^(11a), and—C(O)NR^(11a)R^(11a′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(11a), —OC(O)R^(11a),—OC(O)NR^(11a)R^(11a′), —OS(O)R^(11a), —OS(O)₂R^(11a), —SR^(11a),—S(O)R^(11a), —S(O)₂R^(11a), —S(O)NR^(11a)R^(11a′),—S(O)₂NR^(11a)R^(11a′), —OS(O)NR^(11a)R^(11a′), —OS(O)₂NR^(11a)R^(11a′),—NR^(11a)R^(11a′), —NR^(11a)C(O)R^(12a), —NR^(11a)C(O)OR^(12a),—NR^(11a)C(O)NR^(12a)R^(12a′), —NR^(11a)S(O)R^(12a),—NR^(11a)S(O)₂R^(12a), —NR^(11a)S(O)NR^(12a)R^(12a′),—NR^(11a)S(O)₂NR^(12a)R^(12a′), —C(O)R^(11a), —C(O)OR^(11a) or—C(O)NR^(11a)R^(11a′);

R^(7a) is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl,—C(O)R^(13a), —C(O)OR^(13a) and —C(O)NR^(13a)R^(13a′), wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl is optionally substituted by C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(14a),—OC(O)R^(14a), —OC(O)NR^(14a)R^(14a′), —OS(O)R^(14a), —OS(O)₂R^(14a),—SR^(14a), —S(O)R^(14a), —S(O)₂R^(14a), —S(O)NR^(14a)R^(14a′),—S(O)₂NR^(14a)R^(14a′), —OS(O)NR^(14a)R^(14a′), —OS(O)₂NR^(14a)R^(14a′),—NR^(14a)R^(14a′), —NR^(14a)C(O)R^(15a), —NR^(14a)C(O)OR^(15a),—NR^(14a)C(O)NR^(15a)R^(15a′), —NR^(14a)S(O)R^(15a),—NR^(14a)S(O)₂R^(15a), —NR^(14a)S(O)NR^(15a)R^(15a′),—NR^(14a)S(O)₂NR^(15a)R^(15a′), —C(O)R^(14a), —C(O)OR^(14a) or—C(O)NR^(14a)R^(14a′);

each R^(11a), R^(11a′), R^(12a), R^(12a′), R^(13a), R^(13a′), R^(14a),R^(14a′), R^(15a), R^(15a′), R^(18a), R^(18a′), R^(19a), R^(19a′),R^(20a), R^(20a′), R^(21a) and R^(21a′) is independently selected fromthe group consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl,C₃-C₁₃ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, and5- to 7-membered heteroaryl; and * is a bond. In some embodiments,R^(2a), R^(3a) and R^(4a) are each independently H or C₁-C₆ alkyl;R^(7a) is H or C₁-C₆ alkyl; R^(8a) and R^(9a) are each H, and * is abond.

Where, for example, D¹ is a PBD prodrug as described herein, D² can beany other drug useful for eliciting a desired biological effect. It willbe understood that the identity of D² is not particularly limited, and avariety of drugs known in the art can be used in connection with theconjugates described herein as D². In certain embodiments, D² can be aDNA binding agent. In certain embodiments, D² can be a DNA alkylatingagent. It will be understood that DNA binding agents and DNA alkylatingagents are well known in the art and the identity of such DNA bindingagents and DNA alkylating agents is not limited. In some embodiments, D²can be a DNA minor groove binding drug.

In some embodiments, D² is selected from the group consisting of

wherein

R^(1b), R^(2b), R^(3b) and R^(4b) are each independently selected fromthe group consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(13b), —C(O)OR^(13b), and—C(O)NR^(13b)R^(13b′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(13b), —OC(O)R^(13b),—OC(O)NR^(13b)R^(13b′), —OS(O)R^(13b), —OS(O)₂R^(13b), —SR^(13b),—S(O)R^(13b), —S(O)₂R^(13b), —S(O)NR^(13b)R^(13b′),—S(O)₂NR^(13b)R^(13b′), —OS(O)NR^(13b)R^(13b′), —OS(O)₂NR^(13b)R^(13b′),—NR^(13b)R^(13b′), —NR^(13b)C(O)R^(14b), —NR^(13b)C(O)OR^(14b),—NR^(13b)C(O)NR^(14b)R^(14b′), —NR^(13b)S(O)R^(14b),—NR^(13b)S(O)₂R^(14b), —NR^(13b)S(O)NR^(14b)R^(14b′),—NR^(13b)S(O)₂NR^(14b)R^(14b′), —C(O)R^(13b), —C(O)OR^(13b) or—C(O)NR^(13b)R^(13b′); or any one of R^(1b), R^(2b), R^(3b) and R^(4b)is a bond;

R^(5b), R^(6b) and R^(7b) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(15b), —C(O)OR^(15b), and—C(O)NR^(15b)R^(15b′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, -L⁴H, -L³H, —OR^(15b),—OC(O)R^(15b), —OC(O)NR^(15b)R^(15b′), —OS(O)R^(15b), —OS(O)₂R^(15b),—SR^(15b), —S(O)R^(15b), —S(O)₂R^(15b), —S(O)NR^(15b)R^(15b′),—S(O)₂NR^(15b)R^(15b′), —OS(O)NR^(15b)R^(15b′), —OS(O)₂NR^(15b)R^(15b′),—NR^(15b)R^(15b′), —NR^(15b)C(O)R^(16b), —NR^(15b)C(O)R^(6b),—NR^(15b)C(O)OR^(16b), —NR^(15b)C(O)NR^(16b)R^(16b′),—NR^(15b)S(O)R^(16b), —NR^(15b)S(O)₂R^(16b),—NR^(15b)S(O)NR^(16b)R^(16b′), —NR^(15b)S(O)₂NR^(16b)R^(16b′),—C(O)R^(15b), —C(O)OR^(15b) or —C(O)NR^(15b)R^(15b′); wherein R^(6b) andR^(7b) taken together with the atoms to which they are attachedoptionally combine to form a 3- to 7-membered heterocycloalkyl, orR^(5b) and R^(6b) taken together with the atoms to which they areattached optionally combine to form a 3- to 7-membered heterocycloalkylor 5- to 7-membered heteroaryl, wherein each hydrogen atom in 3- to7-membered heterocycloalkyl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(17b), —OC(O)R¹⁷,—OC(O)NR^(17b)R^(17b′), —OS(O)R¹⁷, —OS(O)₂R¹⁷, —SR^(17b), —S(O)R^(17b),—S(O)₂R^(17b), —S(O)NR^(17b)R^(17b′), —S(O)₂NR^(17b)R^(17b′),—OS(O)NR^(17b)R^(17b′), —OS(O)₂NR^(17b)R^(17b)T, —NR^(17b)R^(17b′),—NR^(17b)C(O)R^(18b), —NR^(17b)C(O)OR^(18b),—NR^(17b)C(O)NR^(18b)R^(18b′), —NR^(17b)S(O)R^(18b),—NR^(17b)S(O)₂R^(18b), —NR^(17b)S(O)NR^(18b)R^(18b′),—NR^(17b)S(O)₂NR^(18b)R^(18b′), —C(O)R¹⁷, —C(O)OR^(17b) or—C(O)NR^(17b)R^(17b); or any one of R^(5b), R^(6b) or R^(7b) is a bond;

R^(8b) and R^(9b) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OR^(19b), —OC(O)R^(19b),—OC(O)NR^(19b)R^(19b′), —OS(O)R^(19b), —OS(O)₂R^(19b), —SR^(19b),—S(O)R^(19b), —S(O)₂R^(19b), —S(O)NR^(19b)R^(19b′),—S(O)₂NR^(19b)R^(9b′), —OS(O)NR^(19b)R^(19b′), —OS(O)₂NR^(19b)R^(19b′),—NR^(19b)R^(19b′), —NR^(19b)C(O)R^(20b), —NR^(19b)C(O)OR^(20b),—NR^(19b)C(O)NR^(2b)R^(20b′), —NR^(19b)S(O)R^(20b),—NR^(19b)S(O)₂R^(20b), —NR^(19b)S(O)NR^(20b)R^(20b′),—NR^(19b)S(O)₂NR^(20b)R^(20b′), —C(O)R^(19b), —C(O)OR^(19b) and—C(O)NR^(19b)R^(19b′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(21b), —OC(O)R^(21b),—OC(O)NR^(21b)R^(21b′), —OS(O)R^(21b), —OS(O)₂R^(21b), —SR^(21b),—S(O)R^(21b), —S(O)₂R^(21b), —S(O)NR^(21b)R^(21b′),—S(O)₂NR^(21b)R^(21b′), —OS(O)NR^(21b)R^(21b′), —OS(O)₂NR^(21b)R^(21b′),—NR^(21b)R^(21b′), —NR^(21b)C(O)R^(22b), —NR^(21b)C(O)OR^(22b),—NR^(21b)C(O)NR^(22b)R^(22b′), —NR^(21b)S(O)R^(22b),—NR^(21b)S(O)₂R^(22b), —NR^(21b)S(O)NR^(22b)R^(22b′),—NR^(21b)S(O)₂NR^(22b)R^(22b′), —C(O)R^(21b), —C(O)OR^(21b) or—C(O)NR^(21b)R^(21b);

R^(10b), R^(11b) and R^(12b) are each independently selected from thegroup consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR^(23b), —OC(O)R^(23b), —OC(O)NR^(23b)R^(23b′),—OS(O)R^(23b), —OS(O)₂R^(23b), —SR^(23b), —S(O)R^(23b), —S(O)₂R^(23b),—S(O)NR^(23b)R^(23b′), —S(O)₂NR^(23b)R^(23b′), —OS(O)NR^(23b)R^(23b′),—OS(O)₂NR^(23b)R^(23b′), —NR^(23b)R^(23b′), —NR^(23b)C(O)R^(24b),—NR^(23b)C(O)OR^(24b), —NR^(23b)C(O)NR^(24b)R^(24b′),—NR^(23b)S(O)R^(24b), —NR^(23b)S(O)₂R^(24b),—NR^(23b)S(O)NR^(24b)R^(24b′), —NR^(23b)S(O)₂NR^(24b)R^(24b′),—C(O)R^(23b), —C(O)OR^(23b) and —C(O)NR^(23b)R^(23b′), wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl is independently optionally substituted by C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(25b),—OC(O)R^(25b), —OC(O)NR^(25b)R^(25b′), —OS(O)R^(25b), —OS(O)₂R^(25b),—SR^(25b), —S(O)R^(25b), —S(O)₂R^(25b), —S(O)NR^(25b)R^(25b′),—S(O)₂NR^(25b)R^(25b′), —OS(O)NR^(25b)R^(25b′), —OS(O)₂NR^(25b)R^(25b′),—NR^(25b)R^(25b′), —NR^(25b)C(O)R^(26b), —NR^(25b)C(O)OR^(26b),—NR^(25b)C(O)NR^(26b)R^(26b′), →NR^(25b)S(O)R^(26b),—NR^(25b)S(O)₂R^(26b), —NR^(25b)S(O)NR^(26b)R^(26b′),—NR^(25b)S(O)₂NR^(26b)R^(26b′), —C(O)R^(25b), —C(O)OR^(25b) or—C(O)NR^(25b)R^(25b), or R^(10b) and R^(11b) taken together with thecarbon atoms to which they are attached optionally combine to form aC₆-C₁₀ aryl, or R^(11b) and R^(12b) taken together with the carbon atomto which they are attached optionally combine to form an exo-methylene;or R^(12b) is absent;

each R^(13b), R^(13b′), R^(14b), R^(14b′), R^(15b), R^(15b′), R^(16b),R^(16b′), R^(17b), R^(17b′), R^(18b), R^(18b′), R^(19b), R^(19b′),R^(20b), R^(20b′), R^(21b), R^(21b′), R^(22b), R^(22b′), R^(23b),R^(23b′), R^(24b), R^(24b′), R^(25b), R^(25b′), R^(26b) and R^(26b′) isindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₁₃ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, C₁-C₆ alkyl(C₆-C₁₀ aryl) and 5- to7-membered heteroaryl, wherein each hydrogen atom in C₆-C₁₀ aryl, C₁-C₆alkyl(C₆-C₁₀ aryl) and 5- to 7-membered heteroaryl is independentlyoptionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OH, —SH, —NH₂, —SO₃H, —C(O)OHand —C(O)NH₂;

provided that one of R^(1b), R^(2b), R^(3b), R^(4b), R^(5b), R^(6b) andR^(7b) is a bond;

R^(1c), R^(2c) and R^(5c) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(6c), —C(O)OR^(6c) and—C(O)NR^(6c)R^(6c′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(7c), —OC(O)R^(7c),—OC(O)NR^(7c)R^(7c′), —OS(O)R^(7c), —OS(O)₂R^(7c), —SR^(7c),—S(O)R^(7c), —S(O)₂R^(7c), —S(O)₂OR^(7c), —S(O)NR^(7c)R^(7c′),—S(O)₂NR^(7c)R^(7c′), —OS(O)NR^(7c)R^(7c′), —OS(O)₂NR^(7c)R^(7c′),—NR^(7c)R^(7c′), —NR^(7c)C(O)R^(8c), —NR^(7c)C(O)OR^(8c),—NR^(7c)C(O)NR^(8c)R^(8c′), —NR^(7c)S(O)R^(8c), —NR^(7c)S(O)₂R^(8c),—NR^(7c)S(O)NR^(8c)R^(8c′), —NR^(7c)S(O)₂NR^(8c)R^(8c′), —C(O)R^(7c),—C(O)OR^(7c) or —C(O)NR^(7c)R^(7c′); or when J is —CR^(13c)═, R^(5c) isabsent; provided that one of R^(1c) or R^(2c) is a bond;

R^(3c) and R^(4c) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OR^(9c), —OC(O)R^(9c),—OC(O)NR^(9c)R^(9c′), —OS(O)R^(9c), —OS(O)₂R^(9c), —SR^(9c),—S(O)R^(9c), —S(O)₂R^(9c), —S(O)NR^(9c)R^(9c′), —S(O)₂NR^(9c)R^(9c′),—OS(O)NR^(9c)R^(9c′), —OS(O)₂NR^(9c)R^(9c′), —NR^(9c)R^(9c′),—NR^(9c)C(O)R^(10c), —NR^(9c)C(O)OR^(10c), —NR^(9c)C(O)NR^(10c)R^(10c′),—NR^(9c)S(O)R^(10c), —NR^(9c)S(O)₂R^(10c), —NR^(9c)S(O)NR^(10c)R^(10c′),—NR^(9c)S(O)₂NR^(10c)R^(10c′), —C(O)R^(9c), —C(O)OR^(9c) and—C(O)NR^(9c)R^(9c′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(11c), —OC(O)R^(11c),—OC(O)NR^(11c)R^(11c′), —OS(O)R^(11c), —OS(O)₂R^(11c), —SR^(11c),—S(O)R^(11c), —S(O)₂R^(11c), —S(O)NR^(11c)R^(11c′),—S(O)₂NR^(11c)R^(11c′), —OS(O)NR^(11c)R^(11c′), —OS(O)₂NR^(11c)R^(11c′),—NR^(11c)R^(11c′), —NR^(11c)C(O)R^(12c), —NR^(11c)C(O)OR^(2c),—NR^(11c)C(O)NR^(2c)R^(12c′), —NR^(11c)S(O)R^(12c),—NR^(11c)S(O)₂R^(12c), —NR^(11c)S(O)NR^(12c)R^(12c′),—NR^(11c)S(O)₂NR^(12c)R^(12c′), —C(O)R^(11c), —C(O)OR^(11c) or—C(O)NR¹¹CR¹¹C;

J is —C(O)—, —CR^(13c)═ or —(CR^(13c)R^(13c′))—

each R^(6c), R^(6c′), R^(7c), R^(7c′), R^(8c), R^(8c′), R^(9c), R^(9c′),R^(10c), R^(10c′), R^(11c), R^(11c′), R^(12c), R^(12c′), R^(13c) andR^(13c′) is independently selected from the group consisting of H, D,C₁-C₇ alkyl, C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-memberedheteroaryl;

R^(1d) is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(2d),—SR^(2d) and —NR^(2d)R^(2d′),

R^(2d) and R^(2d′) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl, wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isoptionally substituted by —OR^(3d), —SR^(3d), and —NR^(3d)R^(3d′);

R^(3d) and R^(3d′) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl;

R^(1e) is selected from the group consisting of H, D, C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl, whereineach hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl is independently optionally substituted by C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(2e),—OC(O)R^(2e), —OC(O)NR^(2e)R^(2e′), —OS(O)R^(2e), —OS(O)₂R^(2e),—SR^(2e), —S(O)R^(2e), —S(O)₂R^(2e), —S(O)NR^(2e)R^(2e′),—S(O)₂NR^(2e)R^(2e′), —OS(O)NR^(2e)R^(2e′), —OS(O)₂NR^(2e)R^(2e′),—NR^(2e)R^(2e′), —NR^(2e)C(O)R^(3e), —NR^(2e)C(O)OR^(3e),—NR^(2e)C(O)NR^(3e)R^(3e′), —NR^(2e)S(O)R^(3e), —NR^(2e)S(O)₂R^(3e),—NR^(2e)S(O)NR^(2e)R^(2e′), —NR^(2e)S(O)₂NR^(3e)R^(3e′), —C(O)R^(2e),—C(O)OR^(2e) or —C(O)NR^(2e)R^(2e);

each R^(2e), R^(2e′), R^(3e) and R^(3e′) is independently selected fromthe group consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5-to 7-membered heteroaryl, wherein each hydrogen atom in C₁-C₆ alkyl,C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isoptionally substituted by —OR^(4e), —SR^(4e) or —NR^(4e)R^(4e′);

R^(4e) and R^(4e′) are independently selected from the group consistingof H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3-to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-memberedheteroaryl;

v is 1, 2 or 3; and

* is a covalent bond.

In some embodiments, Drug can be described by the general formula-D¹-L⁵-D². In some embodiments, Drug can be described by the formula

wherein, L⁵, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a),R^(9a), R^(10a), R^(2b), R^(3b), R^(4b), R^(5b), R^(6b), R^(7b), R^(8b),R^(9b), R^(10b), R^(11b) and R^(12b) are defined as described herein. Insome embodiments, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a),R^(2b), R^(3b), R^(4b), R^(8b) and R^(9b) are H, L⁵ is C₁-C₁₀ alkyl,—(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—, —CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—, —CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹and R^(49′) is H, and u is 1, 2, 3, 4 or 5. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a), R^(10a), R^(2b), R^(3b), R^(4b), R^(8b)and R^(9b) are H, and L⁵ is C₁-C₁₀ alkyl. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a), R^(10a), R^(2b), R^(3b), R^(4b), R^(8b)and R^(9b) are H, L⁵ is —(OCR⁴⁹R⁴⁹CR⁴⁹R^(49′))_(u)—, wherein each R⁴⁹and R^(49′) is H, and u is 4. In some embodiments, R^(4a) is a bond,R^(2a), R^(3a), R^(8a), R^(9a), R^(10a), R^(2b), R^(3b), R^(4b), R^(8b)and R^(9b) are H, L⁵ is C₁-C₁₀ alkyl, —(CR⁴⁹═CR^(49′))—,—(CR⁴⁹R^(49′))_(u)C(O)—, —CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹and R^(49′) is H and u is 1, 2, 3, 4 or 5. In some embodiments, R^(4a)is a bond, R^(2a), R^(3a), R^(8a), R^(9a), R^(10a), R^(2b), R^(3b),R^(4b), R^(8b) and R^(9b) are H, and L⁵ is C₁-C₁₀ alkyl.

In some embodiments, R^(5a) is a bond, R^(2a), R^(3a), R^(4a), R^(8a),R^(9a), R^(10a), R^(2b), R^(3b), R^(4b), R^(8b) and R^(9b) are H, L⁵ isC₁-C₁₀ alkyl, —(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹and R^(49′) is H and u is 1, 2, 3, 4 or 5. In some embodiments, R^(5a)is a bond, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a), R^(2b),R^(3b), R^(4b), R^(8b) and R^(9b) are H, and L⁵ is C₁-C₁₀ alkyl.

In some embodiments, Drug can be described by the general formula-D¹-L⁵-D². In some embodiments, Drug can be described by the formula

wherein L⁵, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a),R^(9a), R^(10a), R^(2c), R^(3c), R^(4c), R^(5c) and J are as definedherein. In some embodiments, R^(2a), R^(3a), R^(4a), R^(5a), R^(9a),R^(10a), R^(2c), R^(3c), R^(4c) and R^(5c) are H, L⁵ is C₁-C₁₀ alkyl,—(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹and R^(49′) is H, and u is 1, 2, 3, 4 or 5. In some embodiments, J is—C(O)—, R^(2a), R^(3a), R^(4a), R^(5a), R^(9a), R^(10a), R^(2c), R^(3c),R^(4c) and R^(5c) are H, and L⁵ is C₁-C₁₀ alkyl. In some embodiments, Jis —CR^(13c)═, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a), R^(2c),R^(3c), R^(4c), R^(5c) and R^(13c) are H, and L⁵ is C₁-C₁₀ alkyl. Insome embodiments, J is —(CR^(13c)R^(13c′))—, R^(2a), R^(3a), R^(4a),R^(8a), R^(9a), R^(10a), R^(2c), R^(3c), R^(4c), R^(5c), R^(13c) andR^(13c′) are H, and L⁵ is C₁-C₁₀ alkyl.

In some embodiments, Drug can be described by the general formula-D¹-L⁵-D². In some embodiments, Drug can be described by the formula

wherein, L⁵, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a),R^(9a) and R^(10a) are as defined herein. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a) and R^(10a) are H, L⁵ is C₁-C₁₀ alkyl,—(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—, —CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—, —CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R⁴⁹CR⁴⁹R^(49′)CR⁴⁹R⁴⁹CR⁴⁹R⁴⁹)_(u)C(O)—, wherein each R⁴⁹and R^(49′) is H, and u is 1, 2, 3, 4 or 5. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a) and R^(10a) are H, and L⁵ is C₁-C₁₀alkyl. In some embodiments, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a) andR^(10a) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ andR^(49′) is H, and u is 3. In some embodiments, R^(2a), R^(3a), R^(4a),R^(8a), R^(9a) and R^(10a) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, whereineach R⁴⁹ and R^(49′) is H, and u is 4. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a) and R^(10a) are H, L⁵ is—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 5.

In some embodiments, Drug can be described by the general formula-D¹-L⁵-D². In some embodiments, Drug can be described by the formula

wherein, L⁵, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a),R^(9a), R^(10a) and R^(1e) are as defined herein. In some embodiments,R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) and R^(1e) are H, L⁵ isC₁-C₁₀ alkyl, —(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—,—CH₂CH₂(OCR⁴⁹R^(49′) CR⁴⁹R^(49′))_(u)—,—CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹and R^(49′) is H, and u is 1, 2, 3, 4 or 5. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) and R^(1e) are H, and L⁵ isC₁-C₁₀ alkyl.

In some embodiments, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) andR^(1e) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ andR^(49′) is H, and u is 3. In some embodiments, R^(2a), R^(3a), R^(4a),R^(8a), R^(9a), R^(10a) and R^(1e) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—,wherein each R⁴⁹ and R^(49′) is H, and u is 4. In some embodiments,R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) and R^(1e) are H, L⁵ is—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 5.

In some embodiments, Drug can be described by the general formula-D¹-L⁵-D². In some embodiments, Drug can be described by the formula

wherein L⁵, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a),R^(9a), R^(10a), R^(1d) and v are as defined herein. In someembodiments, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) and R^(1e)are H, L⁵ is C₁-C₁₀ alkyl, —(CR⁴⁹═CR^(49′))_(u)—,—(CR⁴⁹R^(49′))_(u)C(O)—, —CH₂CH₂(OCR⁴⁹R^(49′) CR⁴⁹R^(49′))_(u)—,—CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹and R^(49′) is H, and u is 1, 2, 3, 4 or 5. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) and R^(1e) are H, and L⁵ isC₁-C₁₀ alkyl. In some embodiments, R^(2a), R^(3a), R^(4a), R^(8a),R^(9a), R^(10a) and R^(1e) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, whereineach R⁴⁹ and R^(49′) is H, and u is 4. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) and R^(1e) are H, L⁵ is—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 5.In some embodiments, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) andR^(1e) are H, L⁵ is C₁-C₁₀ alkyl, and v is 2. In some embodiments,R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) and R^(1e) are H, L⁵ isC₁-C₁₀ alkyl, and v is 3. In some embodiments, R^(2a), R^(3a), R^(4a),R^(8a), R^(9a), R^(10a) and R^(1e) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—,wherein each R⁴⁹ and R^(49′) is H, u is 4, and v is 2. In someembodiments, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) and R^(1e)are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H,u is 4, and v is 3. In some embodiments, R^(2a), R^(3a), R^(4a), R^(8a),R^(9a), R^(10a) and R^(1e) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, whereineach R⁴⁹ and R^(49′) is H, u is 5, and v is 2. In some embodiments,R^(2a), R^(3a), R^(4a), R^(8a), R^(9a), R^(10a) and R^(1e) are H, L⁵ is—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, u is 5, andv is 3.

In some embodiments, Drug can be described by the general formula-D¹-L⁵-D². In some embodiments, Drug can be described by the formula

wherein L⁵, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a),R^(9a) and R^(10a) are as defined herein. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a) and R^(10a) are H, L⁵ is C₁-C₁₀ alkyl,—(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—, —CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—, —CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ andR^(49′) is H, and u is 1, 2, 3, 4 or 5. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a) and R^(10a) are H, and L⁵ is C₁-C₁₀alkyl. In some embodiments, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a) andR^(10a) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ andR^(49′) is H, and u is 4. In some embodiments, R^(2a), R^(3a), R^(4a),R^(8a), R^(9a) and R^(10a) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, whereineach R⁴⁹ and R^(49′) is H, and u is 5.

In some embodiments, Drug can be described by the general formula-D¹-L⁵-D². In some embodiments, Drug can be described by the formula

wherein L⁵, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R⁸, R^(9a)and R^(10a) are as defined herein. In some embodiments, R^(2a), R^(3a),R^(4a), R^(8a), R^(9a) and R^(10a) are H, L⁵ is C₁-C₁₀ alkyl,—(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—, —CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—, —CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ andR^(49′) is H, and u is 1, 2, 3, 4 or 5. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a) and R^(10a) are H, and L⁵ is C₁-C₁₀alkyl. In some embodiments, R^(2a), R^(3a), R^(4a), R^(8a), R^(9a) andR^(10a) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ andR^(49′) is H, and u is 4. In some embodiments, R^(2a), R^(3a), R^(4a),R^(8a), R^(9a) and R^(10a) are H, L⁵ is —(CR⁴⁹R^(49′))_(u)C(O)—, whereineach R⁴⁹ and R^(49′) is H, and u is 5.

In some embodiments, Drug can be described by the general formula-D¹-L⁵-D². In some embodiments, Drug can be described by the formula

wherein L⁵, R^(2a), R^(3a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a),R^(10a), R^(2b), R^(3b), R^(4b), R^(5b), R^(6b), R^(7b), R^(8b), R^(9b),R^(10b), R^(11b) and R^(12b) are defined as described herein. In someembodiments, R^(2a), R^(3a), R^(8a), R^(9a), R^(10a), R^(2b), R^(3b),R^(4b), R^(8b) and R^(9b) are H, L⁵ is C₁-C₁₀ alkyl,—(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—, —CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—, —CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— or—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹and R^(49′) is H, and u is 1, 2, 3, 4 or 5. In some embodiments, R^(2a),R^(3a), R^(4a), R^(8a), R^(9a), R^(10a), R^(2b), R^(3b), R^(4b), R^(8b)and R^(9b) are H, and L⁵ is C₁-C₁₀ alkyl.

In some embodiments, D¹ can be absent. When D¹ is absent, D² is of theformula

wherein

R^(1b), R^(2b), R^(3b) and R^(4b) are each independently selected fromthe group consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(13b), —C(O)OR^(13b), and—C(O)NR^(13b)R^(13b′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(13b), —OC(O)R^(13b),—OC(O)NR^(13b)R^(13b′), —OS(O)R^(13b), —OS(O)₂R^(13b), —SR^(13b),—S(O)R^(13b), —S(O)₂R^(13b), —S(O)NR^(13b)R^(13b′),—S(O)₂NR^(13b)R^(13b′), —OS(O)NR^(13b)R^(13b′), —OS(O)₂NR^(13b)R^(13b′),—NR^(13b)R^(13b′), —NR^(13b)C(O)R^(14b), —NR^(13b)C(O)OR^(14b),—NR^(13b)C(O)NR^(14b)R^(14b′), —NR^(13b)S(O)R^(14b),—NR^(13b)S(O)₂R^(14b), —NR^(13b)S(O)NR^(14b)R^(14b′),—NR^(13b)S(O)₂NR^(14b)R^(14b′), —C(O)R^(13b), —C(O)OR^(13b) or—C(O)NR^(13b)R^(13b′); or any one of R^(1b), R^(2b), R^(3b) and R^(4b)is a bond;

R^(5b), R^(6b) and R^(7b) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —C(O)R^(15b), —C(O)OR^(15b), and—C(O)NR^(15b)R^(15b′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, -L⁴H, -L³H, —OR^(15b),—OC(O)R^(15b), —OC(O)NR^(15b)R^(15b′), —OS(O)R^(15b), —OS(O)₂R^(15b),—SR^(15b), —S(O)R^(15b), —S(O)₂R^(15b), —S(O)NR^(15b)R^(15b′),—S(O)₂NR^(15b)R^(15b′), —OS(O)NR^(15b)R^(15b′), —OS(O)₂NR^(15b)R^(15b′),—NR^(15b)R^(15b′), —NR^(15b)C(O)R^(16b), —NR^(15b)C(O)OR^(16b),—NR^(15b)C(O)NR^(16b)R^(16b′), —NR^(15b)S(O)R^(16b),—NR^(15b)S(O)₂R^(16b), —NR^(15b)S(O)NR^(16b)R^(16b′),—NR^(15b)S(O)₂NR^(16b)R^(16b′), —C(O)R^(15b), —C(O)OR^(15b) or—C(O)NR^(15b)R^(15b′); wherein R^(6b) and R^(7b) taken together with theatoms to which they are attached optionally combine to form a 3- to7-membered heterocycloalkyl, or R^(5b) and R^(6b) taken together withthe atoms to which they are attached optionally combine to form a 3- to7-membered heterocycloalkyl or 5- to 7-membered heteroaryl, wherein eachhydrogen atom in 3- to 7-membered heterocycloalkyl and 5- to 7-memberedheteroaryl is independently optionally substituted by C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(17b),—OC(O)R^(11b), —OC(O)NR^(17b)R^(17b′), —OS(O)R^(17b), —OS(O)₂R^(17b),—SR^(17b), —S(O)R^(17b), —S(O)₂R^(17b), —S(O)NR^(17b)R^(17b′),—S(O)₂NR^(17b)R^(17′), —OS(O)NR^(17b)R^(17b′), —OS(O)₂NR^(17b)R^(17b′),—NR^(17b)R^(17b′), —NR^(17b)C(O)R^(18b), —NR^(17b)C(O)OR^(18b),—NR^(17b)C(O)NR^(18b)R^(18b′), —NR^(17b)S(O)R^(18b),—NR^(17b)S(O)₂R^(18b), —NR^(17b)S(O)NR^(18b)R^(18b′),—NR^(17b)S(O)₂NR^(18b)R^(18b′), —C(O)R^(17b), —C(O)OR^(17b) or—C(O)NR^(17b)R^(17b); or any one of R^(5b), R^(6b) or R^(7b) is a bond;

R^(8b) and R^(9b) are each independently selected from the groupconsisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OR^(19b), —OC(O)R^(19b),—OC(O)NR^(19b)R^(19b′), —OS(O)R^(19b), —OS(O)₂R^(19b), —SR^(19b),—S(O)R^(19b), —S(O)₂R^(19b), —S(O)NR^(19b)R^(19b′),—S(O)₂NR^(19b)R^(19b′), —OS(O)NR^(19b)R^(19b′), —OS(O)₂NR^(19b)R^(19b′),—NR^(19b)R^(19b′), —NR^(19b)C(O)R^(20b), —NR^(19b)C(O)OR^(20b),—NR^(19b)C(O)NR^(2b)R^(20b′), —NR^(19b)S(O)R^(20b),—NR^(19b)S(O)₂R^(20b), —NR^(19b)S(O)NR^(2b)R^(20b′),—NR^(19b)S(O)₂NR^(20b)R^(20b′), —C(O)R^(19b), —C(O)OR^(19b) and—C(O)NR^(19b)R^(19b′), wherein each hydrogen atom in C₁-C₆ alkyl, C₂-C₆alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl and 5- to 7-membered heteroaryl isindependently optionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(21b), —OC(O)R^(21b),—OC(O)NR^(21b)R^(21b′), —OS(O)R^(21b), —OS(O)₂R^(21b), —SR^(21b),—S(O)R^(21b), —S(O)₂R^(21b), —S(O)NR^(21b)R^(21b′),—S(O)₂NR^(21b)R^(21b′), —OS(O)NR^(21b)R^(21b′), —OS(O)₂NR^(21b)R^(21b′),—NR^(21b)R^(21b′), —NR^(21b)C(O)R^(22b), —NR^(21b)C(O)OR^(22b),—NR^(21b)C(O)NR^(22b)R^(22b′), —NR^(21b)S(O)R^(22b),—NR^(21b)S(O)₂R^(22b), —NR^(21b)S(O)NR^(22b)R^(22b′),—NR^(21b)S(O)₂NR^(22b)R^(22b′), —C(O)R^(21b), —C(O)OR^(21b) or—C(O)NR^(21b)R^(21b);

R^(10b), R^(11b) and R^(12b) are each independently selected from thegroup consisting of H, D, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —OR^(23b), —OC(O)R^(23b), —OC(O)NR^(23b)R^(23b′),—OS(O)R^(23b), —OS(O)₂R^(23b), —SR^(23b), —S(O)R^(23b), —S(O)₂R^(23b),—S(O)NR^(23b)R^(23b′), —S(O)₂NR^(23b)R^(23b′), —OS(O)NR^(23b)R^(23b′),—OS(O)₂NR^(23b)R^(23b′), —NR^(23b)R^(23b′), —NR^(23b)C(O)R^(24b),—NR^(23b)C(O)OR^(24b), —NR^(23b)C(O)NR^(24b)R^(24b′),—NR^(23b)S(O)R^(24b), —NR^(23b)S(O)₂R^(24b),—NR^(23b)S(O)NR^(24b)R^(24b′), —NR^(23b)S(O)₂NR^(24b)R^(24b′),—C(O)R^(23b), —C(O)OR^(23b) and —C(O)NR^(23b)R^(23b′), wherein eachhydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl and 5- to7-membered heteroaryl is independently optionally substituted by C₁-C₆alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl, —OR^(25b),—OC(O)R^(25b), —OC(O)NR^(25b)R^(25b′), —OS(O)R^(25b), —OS(O)₂R^(25b),—SR^(25b), —S(O)R^(25b), —S(O)₂R^(25b), —S(O)NR^(25b)R^(25b′),—S(O)₂NR^(25b)R^(25b′), —OS(O)NR^(25b)R^(25b′), —OS(O)₂NR^(25b)R^(25b′),—NR^(25b)R^(25b′), —NR^(25b)C(O)R^(26b), —NR^(25b)C(O)OR^(26b),—NR^(25b)C(O)NR^(26b)R^(26b′), —NR^(25b)S(O)R^(26b),—NR^(25b)S(O)₂R^(26b), —NR^(25b)S(O)NR^(26b)R^(26b′),—NR^(25b)S(O)₂NR^(26b)R^(26b′), —C(O)R^(25b), —C(O)OR^(25b) or—C(O)NR^(25b)R^(25b), or R^(10b) and R^(11b) taken together with thecarbon atoms to which they are attached optionally combine to form aC₆-C₁₀ aryl, or R^(11b) and R^(12b) taken together with the carbon atomto which they are attached optionally combine to form an exo-methylene;or R^(12b) is absent;

each R^(13b), R^(13b′), R^(14b), R^(14b′), R^(15b), R^(15b′), R^(16b),R^(16b′), R^(17b), R^(17b′), R^(18b), R^(18b′), R^(19b), R^(19b′),R^(20b), R^(20b′), R^(21b), R^(21b′), R^(22b), R^(22b′), R^(23b),R^(23b′), R^(24b), R^(24b′), R^(25b), R^(25b′), R^(26b) and R^(26b′) isindependently selected from the group consisting of H, D, C₁-C₇ alkyl,C₂-C₇ alkenyl, C₂-C₇ alkynyl, C₃-C₁₃ cycloalkyl, 3- to 7-memberedheterocycloalkyl, C₆-C₁₀ aryl, C₁-C₆ alkyl(C₆-C₁₀ aryl) and 5- to7-membered heteroaryl, wherein each hydrogen atom in C₆-C₁₀ aryl, C₁-C₆alkyl(C₆-C₁₀ aryl) and 5- to 7-membered heteroaryl is independentlyoptionally substituted by C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl,C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to7-membered heteroaryl, —CN, —NO₂, —NCO, —OH, —SH, —NH₂, —SO₃H, —C(O)OHand —C(O)NH₂; and * is a bond.

The conjugates described herein can be used for both human clinicalmedicine and veterinary applications. Thus, the host animal harboringthe population of pathogenic cells and treated with the conjugatesdescribed herein can be human or, in the case of veterinaryapplications, can be a laboratory, agricultural, domestic, or wildanimal. The conjugates described herein can be applied to host animalsincluding, but not limited to, humans, laboratory animals such rodents(e.g., mice, rats, hamsters, etc.), rabbits, monkeys, chimpanzees,domestic animals such as dogs, cats, and rabbits, agricultural animalssuch as cows, horses, pigs, sheep, goats, and wild animals in captivitysuch as bears, pandas, lions, tigers, leopards, elephants, zebras,giraffes, gorillas, dolphins, and whales.

The conjugate, compositions, methods, and uses described herein areuseful for treating diseases caused at least in part by populations ofpathogenic cells, which may cause a variety of pathologies in hostanimals. As used herein, the term “pathogenic cells” or “population ofpathogenic cells” generally refers to cancer cells, infectious agentssuch as bacteria and viruses, bacteria- or virus-infected cells,inflammatory cells, activated macrophages capable of causing a diseasestate, and any other type of pathogenic cells that uniquely express,preferentially express, or overexpress cell surface receptors or cellsurface antigens that may be bound by or targeted by the conjugatesdescribed herein. Pathogenic cells can also include any cells causing adisease state for which treatment with the conjugates described hereinresults in reduction of the symptoms of the disease. For example, thepathogenic cells can be host cells that are pathogenic under somecircumstances such as cells of the immune system that are responsiblefor graft versus host disease, but not pathogenic under othercircumstances.

Thus, the population of pathogenic cells can be a cancer cell populationthat is tumorigenic, including benign tumors and malignant tumors, or itcan be non-tumorigenic. The cancer cell population can arisespontaneously or by such processes as mutations present in the germlineof the host animal or somatic mutations, or it can be chemically-,virally-, or radiation-induced. The conjugates described herein can beutilized to treat such cancers as carcinomas, sarcomas, lymphomas,Hodgekin's disease, melanomas, mesotheliomas, Burkitt's lymphoma,nasopharyngeal carcinomas, leukemias, and myelomas. The cancer cellpopulation can include, but is not limited to, oral, thyroid, endocrine,skin, gastric, esophageal, laryngeal, pancreatic, colon, bladder, bone,ovarian, cervical, uterine, breast, testicular, prostate, rectal,kidney, liver, and lung cancers.

The disclosure includes all pharmaceutically acceptableisotopically-labelled conjugates, and their Drug(s) incorporatedtherein, wherein one or more atoms are replaced by atoms having the sameatomic number, but an atomic mass or mass number different from theatomic mass or mass number which predominates in nature.

Examples of isotopes suitable for inclusion in the conjugates, and theirDrug(s) incorporated therein, include isotopes of hydrogen, such as ²Hand ³H, carbon, such as ¹¹C, ¹³C and ¹⁴C, chlorine, such as ³⁶Cl,fluorine, such as ¹⁸F, iodine, such as ¹²³I and ¹²⁵I, nitrogen, such as¹³N and ¹⁵N, oxygen, such as ¹⁵O, ¹⁷O and ¹⁸O, phosphorus, such as ³²P,and sulfur, such as ³⁵S.

Certain isotopically-labelled conjugates, and their Drug(s) incorporatedtherein, for example, those incorporating a radioactive isotope, areuseful in drug and/or substrate tissue distribution studies. Theradioactive isotopes tritium, i.e. ³H, and carbon-14, i.e. ¹⁴C, areparticularly useful for this purpose in view of their ease ofincorporation and ready means of detection.

Substitution with heavier isotopes such as deuterium, i.e. ²H, mayafford certain therapeutic advantages resulting from greater metabolicstability, for example, increased in vivo half-life or reduced dosagerequirements, and hence may be preferred in some circumstances.

Substitution with positron emitting isotopes, such as ¹¹C, ¹⁸F, and ¹³N,can be useful in Positron Emission Topography (PET) studies forexamining substrate receptor occupancy. Isotopically-labeled conjugates,and their Drug(s) incorporated therein, can generally be prepared byconventional techniques known to those skilled in the art or byprocesses analogous to those described in the accompanying Examplesusing an appropriate isotopically-labeled reagents in place of thenon-labeled reagent previously employed.

The conjugates and compositions described herein may be administeredorally. Oral administration may involve swallowing, so that theconjugate or composition enters the gastrointestinal tract, or buccal orsublingual administration may be employed by which the conjugate orcomposition enters the blood stream directly from the mouth.

Formulations suitable for oral administration include solid formulationssuch as tablets, capsules containing particulates, liquids, or powders,lozenges (including liquid-filled), chews, multi- and nano-particulates,gels, solid solution, liposome, films, ovules, sprays and liquidformulations.

Liquid formulations include suspensions, solutions, syrups and elixirs.Such formulations may be employed as fillers in soft or hard capsulesand typically comprise a carrier, for example, water, ethanol,polyethylene glycol, propylene glycol, methylcellulose, or a suitableoil, and one or more emulsifying agents and/or suspending agents. Liquidformulations may also be prepared by the reconstitution of a solid, forexample, from a sachet.

The conjugates and compositions described herein may also be used infast-dissolving, fast-disintegrating dosage forms such as thosedescribed in Expert Opinion in Therapeutic Patents, 11 (6), 981-986, byLiang and Chen (2001). For tablet dosage forms, depending on dose, theconjugate may make up from 1 weight % to 80 weight % of the dosage form,more typically from 5 weight % to 60 weight % of the dosage form. Inaddition to the conjugates and compositions described herein, tabletsgenerally contain a disintegrant. Examples of disintegrants includesodium starch glycolate, sodium carboxymethyl cellulose, calciumcarboxymethyl cellulose, croscarmellose sodium, crospovidone,polyvinylpyrrolidone, methyl cellulose, microcrystalline cellulose,lower alkyl-substituted hydroxypropyl cellulose, starch, pregelatinisedstarch and sodium alginate. Generally, the disintegrant will comprisefrom 1 weight % to 25 weight %, preferably from 5 weight % to 20 weight% of the dosage form.

Binders are generally used to impart cohesive qualities to a tabletformulation. Suitable binders include microcrystalline cellulose,gelatin, sugars, polyethylene glycol, natural and synthetic gums,polyvinylpyrrolidone, pregelatinised starch, hydroxypropyl cellulose andhydroxypropyl methylcellulose. Tablets may also contain diluents, suchas lactose (monohydrate, spray-dried monohydrate, anhydrous and thelike), mannitol, xylitol, dextrose, sucrose, sorbitol, microcrystallinecellulose, starch and dibasic calcium phosphate dihydrate.

Tablets may also optionally comprise surface active agents, such assodium lauryl sulfate and polysorbate 80, and glidants such as silicondioxide and talc. When present, surface active agents may comprise from0.2 weight % to 5 weight % of the tablet, and glidants may comprise from0.2 weight % to 1 weight % of the tablet.

Tablets also generally contain lubricants such as magnesium stearate,calcium stearate, zinc stearate, sodium stearyl fumarate, and mixturesof magnesium stearate with sodium lauryl sulphate. Lubricants generallycomprise from 0.25 weight % to 10 weight %, preferably from 0.5 weight %to 3 weight % of the tablet.

Other possible ingredients include anti-oxidants, colorants, flavoringagents, preservatives and taste-masking agents. Exemplary tabletscontain up to about 80% drug, from about 10 weight % to 25 about 90weight % binder, from about 0 weight % to about 85 weight % diluent,from about 2 weight % to about 10 weight % disintegrant, and from about0.25 weight % to about 10 weight % lubricant.

Tablet blends may be compressed directly or by roller to form tablets.Tablet blends or portions of blends may alternatively be wet-, dry-, ormelt-granulated, melt congealed, or extruded before tableting. The finalformulation may comprise one or more layers and may be coated oruncoated; it may even be encapsulated. The formulation of tablets isdiscussed in Pharmaceutical Dosage Forms: Tablets, Vol. 1, by H.Lieberman and L. Lachman (Marcel Dekker, New York, 1980).

Consumable oral films for human or veterinary use are typically pliablewater-soluble or water-swellable thin film dosage forms which may berapidly dissolving or mucoadhesive and typically comprise a conjugate asdescribed herein, a film-forming polymer, a binder, a solvent, ahumectant, a plasticizer, a stabilizer or emulsifier, aviscosity-modifying agent and a solvent. Some components of theformulation may perform more than one function.

Solid formulations for oral administration may be formulated to beimmediate and/or modified release. Modified release formulations includedelayed-, sustained-, pulsed-, controlled-, targeted and programmedrelease. Suitable modified release formulations for the purposes of thedisclosure are described in U.S. Pat. No. 6,106,864. Details of othersuitable release technologies such as high energy dispersions andosmotic and coated particles are to be found in PharmaceuticalTechnology On-line, 25(2), 1-14, by Verma et al (2001). The use ofchewing gum to achieve controlled release is described in WO 00/35298.

The conjugates described herein can also be administered directly intothe blood stream, into muscle, or into an internal organ. Suitable meansfor parenteral administration include intravenous, intraarterial,intraperitoneal, intrathecal, intraventricular, intraurethral,intrasternal, intracranial, intramuscular and subcutaneous.

Suitable devices for parenteral administration include needle (includingmicro-needle) injectors, needle-free injectors and infusion techniques.Parenteral formulations are typically aqueous solutions which maycontain excipients such as salts, carbohydrates and buffering agents(preferably to a pH of from 3 to 9), but, for some applications, theymay be more suitably formulated as a sterile non-aqueous solution or asa dried form to be used in conjunction with a suitable vehicle such assterile, pyrogen-free water.

The preparation of parenteral formulations under sterile conditions, forexample, by lyophilisation, may readily be accomplished using standardpharmaceutical techniques well known to those skilled in the art. Thesolubility of conjugates described herein used in the preparation ofparenteral solutions may be increased by the use of appropriateformulation techniques, such as the incorporation ofsolubility-enhancing agents.

Formulations for parenteral administration may be formulated to beimmediate and/or modified release. Modified release formulations includedelayed-, sustained-, pulsed-, controlled-, targeted and programmedrelease. Thus conjugates described herein can be formulated as a solid,semi-solid, or thixotropic liquid for administration as an implanteddepot providing modified release of the active compound. Examples ofsuch formulations include drug-coated stents andpoly(lactic-coglycolic)acid (PGLA) microspheres. The conjugatesdescribed herein can also be administered topically to the skin ormucosa, that is, dermally or transdermally. Typical formulations forthis purpose include gels, hydrogels, lotions, solutions, creams,ointments, dusting powders, dressings, foams, films, skin patches,wafers, implants, sponges, fibres, bandages and microemulsions.Liposomes may also be used. Typical carriers include alcohol, water,mineral oil, liquid petrolatum, white petrolatum, glycerin, polyethyleneglycol and propylene glycol. Penetration enhancers may beincorporated—see, for example, J. Pharm Sci, 88 (10), 955-958 by Finninand Morgan (October 1999). Other means of topical administration includedelivery by electroporation, iontophoresis, phonophoresis, sonophoresisand microneedle or needle-free (e.g. Powderject™, Bioject™, etc.)injection.

Formulations for topical administration may be formulated to beimmediate and/or modified release. Modified release formulations includedelayed-, sustained-, pulsed-, controlled-, targeted and programmedrelease. The conjugates described herein can also be administeredintranasally or by inhalation, typically in the form of a dry powder(either alone, as a mixture, for example, in a dry blend with lactose,or as a mixed component particle, for example, mixed with phospholipids,such as phosphatidylcholine) from a dry powder inhaler or as an aerosolspray from a pressurized container, pump, spray, atomizer (preferably anatomizer using electrohydrodynamics to produce a fine mist), ornebulizer, with or without the use of a suitable propellant, such as1,1,1,2-tetrafluoroethane or 1,1,1,2,3,3,3-heptafluoropropane. Forintranasal use, the powder may comprise a bioadhesive agent, forexample, chitosan or cyclodextrin. The pressurized container, pump,spray, atomizer, or nebulizer contains a solution or suspension of theconjugates(s) of the present disclosure comprising, for example,ethanol, aqueous ethanol, or a suitable alternative agent fordispersing, solubilizing, or extending release of the active, apropellant(s) as solvent and an optional surfactant, such as sorbitantrioleate, oleic acid, or an oligolactic acid. Prior to use in a drypowder or suspension formulation, the conjugate is micronized to a sizesuitable for delivery by inhalation (typically less than 5 microns).This may be achieved by any appropriate comminuting method, such asspiral jet milling, fluid bed jet milling, supercritical fluidprocessing to form nanoparticles, high pressure homogenization, or spraydrying. Capsules (made, for example, from gelatin orhydroxypropylmethylcellulose), blisters and cartridges for use in aninhaler or insufflator may be formulated to contain a powder mix of theconjugate described herein, a suitable powder base such as lactose orstarch and a performance modifier such as Iso-leucine, mannitol, ormagnesium stearate.

The lactose may be anhydrous or in the form of the monohydrate,preferably the latter. Other suitable excipients include dextran,glucose, maltose, sorbitol, xylitol, fructose, sucrose and trehalose. Atypical formulation may comprise a conjugate of the present disclosure,propylene glycol, sterile water, ethanol and sodium chloride.Alternative solvents which may be used instead of propylene glycolinclude glycerol and polyethylene glycol.

The conjugates described here can be combined with solublemacromolecular entities, such as cyclodextrin and suitable derivativesthereof or polyethylene glycol-containing polymers, in order to improvetheir solubility, dissolution rate, taste-masking, bioavailabilityand/or stability for use in any of the aforementioned modes ofadministration.

Drug-cyclodextrin complexes, for example, are found to be generallyuseful for most dosage forms and administration routes. Both inclusionand non-inclusion complexes may be used. As an alternative to directcomplexation with the drug, the cyclodextrin may be used as an auxiliaryadditive, i.e. as a carrier, diluent, or solubilizer. Most commonly usedfor these purposes are alpha-, beta- and gamma-cyclodextrins, examplesof which may be found in International Patent Applications Nos. WO91/11172, WO 94/02518 and WO 98/55148.

Inasmuch as it may desirable to administer a combination of activecompounds, for example, for the purpose of treating a particular diseaseor condition, it is within the scope of the present disclosure that twoor more pharmaceutical compositions, at least one of which contains aconjugate as described herein, may conveniently be combined in the formof a kit suitable for co-administration of the compositions. Thus thekit of the present disclosure comprises two or more separatepharmaceutical compositions, at least one of which contains a conjugateas described herein, and means for separately retaining saidcompositions, such as a container, divided bottle, or divided foilpacket. An example of such a kit is the familiar blister pack used forthe packaging of tablets, capsules and the like. The kit of the presentdisclosure is particularly suitable for administering different dosageforms, for example parenteral, for administering the separatecompositions at different dosage intervals, or for titrating theseparate compositions against one another. To assist compliance, the kittypically comprises directions for administration and may be providedwith a so-called memory aid.

EXAMPLES Chemical Examples

It is to be understood that the conjugates described herein wereprepared according to the processes described herein and/or conventionalprocesses. Illustratively, the stereocenters of the conjugates describedherein may be substantially pure (S), the substantially pure (R), or anymixture of (S) and (R) at any asymmetric carbon atom, and each may beused in the processes described herein. Similarly, the processesdescribed in these illustrative examples may be adapted to prepare otherconjugates described herein by carrying out variations of the processesdescribed herein with routine selection of alternative startingmaterials and reagents. It is also to be understood that radicals ofthese examples are included in the PBD prodrugs, poly-PBD prodrugs,mixed PBDs, conjugates, and conjugates described herein.

Example: Process for Preparing Intermediate Proline Derivatives

Example: Process for Preparing Intermediate Mono Fmoc-proPBD

Example: Process for Preparing proPBD-SN-38

Example. Process for Preparing EC1879

Example. Process for Preparing EC1884

Example. Process for Preparing MC-VA-PAB Linked proPBD-FmocPBD

Example. Processes for Modification of Enantiomers of ProlineDerivatives

It is to be further understood that the processes described herein forparticular example conjugates are illustrative of the general processes,and each may be adapted for preparing other example conjugates describedherein. For example, it is to be understood that the correspondingpreparations using D-proline, L-proline, or proline of varying opticalmixtures, including racemic proline, is also described herein. Forexample, olefination and reduction of D-proline, L-proline, or prolineis described herein as follows:

Example. Synthesis of EC2177

MOM ether EC2173 was synthesized in 58% yield following the proceduredescribed in Boger, D. L.; Hughes, T. V.; Hedrick, H. P. J Org. Chem.2001, 66, 2207-2216. ¹H NMR (500 MHz, CDCl₃): δ 8.20-8.09 (m, 1H),7.74-7.66 (m, 1H), 7.43 (ddd, J=8.3, 6.8, 1.3 Hz, 1H), 7.35 (ddd, J=8.2,6.8, 1.2 Hz, 1H), 7.05 (d, J=2.0 Hz, 1H), 6.90-6.82 (m, 1H), 6.72 (s,1H), 5.36 (s, 2H), 3.53 (s, 3H), 1.54 (s, 9H). [M+H]⁺=Calculated 304.16,found 304.1

EC2174 was synthesized in 54% yield following the procedure described inBoger, D. L.; Hughes, T. V.; Hedrick, H. P. J. Org. Chem. 2001, 66,2207-2216. ¹H NMR (500 MHz, CDCl₃): δ 8.21 (dd, J=8.4, 1.3 Hz, 1H),8.10-7.98 (m, 2H), 7.54 (ddd, J=8.5, 6.8, 1.4 Hz, 1H), 7.42 (ddd, J=8.2,6.8, 1.1 Hz, 1H), 7.32-7.16 (m, 1H), 5.46 (s, 2H), 3.58 (s, 3H), 1.59(s, 9H). [M+H]⁺=Calculated 430.05, found 430.08

Allyl chloride EC2175 was synthesized in 48% yield following theprocedure described in Boger, D. L.; Hughes, T. V.; Hedrick, H. P. J.Org. Chem. 2001, 66, 2207-2216. ¹H NMR (500 MHz, CDCl₃): δ 8.30-8.14 (m,2H), 7.64-7.45 (m, 2H), 6.99 (s, 1H), 6.18-6.03 (m, 2H), 5.37 (s, 2H),4.68-4.55 (m, 1H), 4.31 (dd, J=15.8, 6.8 Hz, 1H), 3.53 (s, 3H), 1.35 (s,9H). [M+H]⁺=Calculated 504.05, found 504.06

EC2176 was synthesized in 78% yield following the procedure described inBoger, D. L.; Hughes, T. V.; Hedrick, H. P. J. Org. Chem. 2001, 66,2207-2216. ¹H NMR (500 MHz, CDCl₃): δ 8.29-8.20 (m, 1H), 7.92 (s, 1H),7.67 (dd, J=24.1, 8.3 Hz, 1H), 7.49 (dddd, J=16.4, 8.3, 6.8, 1.3 Hz,1H), 7.35 (tdd, J=8.2, 7.5, 1.2 Hz, 1H), 5.42 (s, 2H), 4.15 (ddd,J=22.0, 15.5, 10.1 Hz, 1H), 4.00-3.88 (m, 1H), 3.75-3.66 (m, 1H), 3.56(d, J=1.5 Hz, 3H), 1.63 (s, 9H). [M+H]⁺=Calculated 378.15, found 378.15

EC2177 was synthesized in 64% yield following the procedure described inBoger, D. L.; Hughes, T. V.; Hedrick, H. P. J. Org. Chem. 2001, 66,2207-2216. ¹H NMR (500 MHz, CDCl₃): δ 8.20 (t, J=8.2 Hz, 1H), 7.81 (s,1H), 7.65 (dd, J=24.5, 8.4 Hz, 1H), 7.53-7.41 (m, 1H), 7.37-7.28 (m,1H), 4.22-4.05 (m, 1H), 4.00-3.87 (m, 1H), 3.83-3.64 (m, 1H), 1.61 (d,J=6.3 Hz, 9H).

EC2178 was synthesized following the procedure described Wang, Y.; Li,L.; Tian, Z.; Jiang, W.; Larrick, J. W. Bioorg. Med. Chem. 2006, 14,7854-7861. ¹HNMR (500 MHz, CDCl₃): δ 8.24-8.17 (m, 2H), 8.15 (dd, J=9.2,2.5 Hz, 2H), 7.49-7.42 (m, 2H), 7.42-7.34 (m, 1H), 7.28-7.20 (m, 1H),4.34-4.18 (m, 1H), 4.15-4.03 (m, 1H), 3.97 (td, J=9.2, 3.8 Hz, 1H),3.91-3.82 (m, 1H), 3.53-3.41 (m, 1H), 3.36-3.23 (m, 1H), 1.56 (s, 9H).[M+H]⁺=Calculated 499.12, found 499.02

EC2179 was synthesized following the procedure described in Wang, Y.;Li, L.; Tian, Z.; Jiang, W.; Larrick, J. W. Bioorg. Med. Chem. 2006, 14,7854-7861. ¹H NMR (500 MHz, CDCl₃): δ 7.88 (s, 1H), 7.75 (d, J=8.4 Hz,1H), 7.57 (d, J=8.3 Hz, 1H), 7.37 (ddd, J=8.2, 6.7, 1.2 Hz, 1H),7.30-7.22 (m, 1H), 4.23-4.08 (m, 1H), 4.01 (dd, J=11.8, 8.7 Hz, 1H),3.95-3.84 (m, 1H), 3.81 (dd, J=11.1, 3.3 Hz, 1H), 3.74 (s, 2H), 3.54 (s,2H), 3.37 (t, J=10.7 Hz, 1H), 2.47-2.33 (m, 4H), 2.27 (s, 3H), 1.50 (s,9H). [M+H]⁺=Calculated 460.98, found 460.20

EC2189 was prepared as described herein. ¹H NMR (500 MHz, CDCl₃): δ 8.37(s, 1H), 7.87 (d, J=8.4 Hz, 1H), 7.71 (d, J=8.4 Hz, 1H), 7.52 (ddd,J=8.1, 6.7, 1.2 Hz, 1H), 7.41 (ddd, J=8.0, 6.8, 1.1 Hz, 1H), 7.06 (d,J=1.9 Hz, 1H), 7.01 (d, J=1.9 Hz, 1H), 4.37-4.18 (m, 2H), 4.06 (t, J=6.5Hz, 3H), 3.95 (dd, J=11.2, 3.3 Hz, 1H), 3.86 (s, 3H), 3.85 (s, 3H),3.69-3.62 (m, 2H), 3.45 (t, J=10.9 Hz, 1H), 2.56 (dt, J=24.1, 17.9 Hz,6H), 2.40 (s, 3H), 1.84 (p, J=6.9 Hz, 5H), 1.67-1.56 (m, 2H).[M+H]⁺=Calculated 653.28, found 653.29

To ester EC2189 (72 mg, 0.11 mmol) in a THF/MeOH/H₂O (3:1:1, 1 ml) wasadded LiOH (1.1 ml, 1.1 mmol). The reaction was allowed to stir at roomtemperature and monitored by LCMS. Upon completion the reaction mixturewas acidified to pH 2 with 1M HCl and the volatile solvents were removedvia reduced pressure. The product was purified by low pressurechromatography using C18 stationary phase and eluting with H₂O andacetonitrile, followed by lyophilization to yield the desired acidEC2190 (42 mg, 60%) as a colorless oil. ¹H NMR (500 MHz, CDCl₃) Pivotalsignals: δ 8.31-8.20 (m, 1H), 7.81-7.72 (m, 1H), 7.66 (d, J=8.4 Hz, 1H),7.52-7.41 (m, 1H), 7.40-7.30 (m, 1H), 7.11-7.01 (m, 1H), 7.01-6.92 (m,1H), 4.22 (dd, J=23.9, 10.0 Hz, 3H), 4.07-3.91 (m, 4H), 3.90-3.81 (m,2H), 3.78 (s, 3H). [M+H]⁺=Calculated 639.26, found 639.30

Boc amine EC1693 (21 mg, 44.1 μmol) was dissolved in a 50:50 TFA:CH₂Cl₂solution and stirred for 30 mins. The solvent was removed in vacuo andthe residue was taken in saturated NaHCO₃ and extracted with ethylacetate three times. The organic extracts were combined, dried overNa₂SO₄, filtered and the solvent was removed to yield the amine. Thecrude amine was dissolved in DMF (2 ml) and transferred onto acid EC2190(18.8 mg, 29.4 μmol) under Argon atmosphere. To the solution were addedPyBOP (33.6 mg, 64.7 μmol), DIPEA (31.5 μl, 0.177 mmol) and left to stirfor 5 hours. Upon completion, the reaction was diluted with water (10ml), saturated NH₄Cl (10 ml) and extracted with ethyl acetate threetimes. The organic extracts were combined, dried over Na₂SO₄, filteredand the solvent was removed via reduced pressure. The product waspurified using silica gel chromatography with dichloromethane andmethanol as the eluent to yield the desired amide EC2191 (23 mg, 79%).¹H NMR (500 MHz, CDCl₃) Pivotal signals: δ 8.36 (s, 1H), 8.26 (s, 1H),7.77 (d, J=8.4 Hz, 1H), 7.67-7.50 (m, 3H), 7.43 (t, J=7.6 Hz, 1H), 7.33(t, J=7.6 Hz, 1H), 7.29-7.20 (m, 2H), 7.07-6.94 (m, 1H), 6.42 (t, J=15.6Hz, 1H), 5.14-4.77 (m, 3H), 4.34-4.14 (m, 3H), 3.73 (s, 3H), 2.42 (s,3H), 2.30-2.10 (m, 1H). [M+H]⁺=Calculated 988.35, found 988.45

EC2176 was separated into (R)- EC2176 and (S)- EC217 using Normal phaseHPLC on Chiral Stationary Phase was used for chiral separation ofracemic EC 2176. Conditions as follows: Column Name: (S,S)-Whelk-O1,Column Size: 250 mm×4.6 mm, Mobile Phase: Hexane/IPA (70/30).

Boc amine, (S)-EC2176 (49 mg, 0.13 mmol) was dissolved in a 30% TFA inCH₂Cl₂ solution (5 ml) at 0° C. and let stir for 3 hr. LCMS was used tomonitor the reaction until complete deprotection. The reaction mixturewas quenched with saturated NaHCO₃ and extracted three times with ethylacetate. The organic extracts were combined, dried over Na₂SO₄, filteredand the solvent was removed under vacuum to yield the crude amine. Theamine and EC2180 (40 mg, 0.13 mmol) were dissolved in DMF (1 ml) underAgron atmosphere. To the reaction mixture, PyBOP (134 mg, 0.26 mmol) wasadded followed by DIPEA (0.114 ml, 0.65 mmol) and the reaction mixturewas stirred for 5 hours. The reaction mixture was quenched withsaturated NH₄Cl and extracted three times with ethyl acetate. Theorganic extracts were combined, dried over Na₂SO₄, filtered, the solventwas removed under vacuum and EC2256 was purified using silica gelchromatography to yield the desired amide (20 mg, 28%).[M+H]⁺=Calculated 571.21, found 571.30

Ester EC2256 (19 mg, 0.033 mmol) was dissolved in a 3:1:1 mixture ofTHF:H₂O:MeOH (1 ml) and LiOH (0.33 ml, 0.33 mmol) was added. Thereaction was monitored until full conversion was complete. The organicsolvents were removed under vacuum and the crude product was purified bylow pressure chromatography using C18 stationary phase and eluted withH₂O and ACN.

Fractions of the desired product were combined, CAN was removed, theaqueous layer was extracted with ethyl acetate, dried over Na₂SO₄ andconcentrated to yield acid EC2257 (17.5 mg, 94%). [M+H]⁺=Calculated558.03, found 557.31

Boc amine, EC1693 (19 mg, 0.04 mmol) was dissolved in a 50% TFA inCH₂Cl₂ solution (5 ml) at 0° C. and stirred for 3 hr. LCMS was used tomonitor the reaction until deprotection was complete. The reactionmixture was quenched with saturated NaHCO₃ and extracted three timeswith ethyl acetate. The organic extracts were combined, dried overNa₂SO₄, filtered and the solvent was removed under vacuum to yield thecrude amine. The amine and EC2257 (17.5 mg, 0.03 mmol) were dissolved inDMF (1 ml) under Argon atmosphere. To the reaction mixture, PyBOP (36mg, 0.07 mmol) was added followed by DIPEA (0.033 ml, 0.19 mmol), andthe reaction mixture was stirred for 5 hours. The reaction mixture wasquenched with saturated NH₄Cl and extracted three times with ethylacetate. The organic extracts were combined, dried over Na₂SO₄,filtered, the solvent was removed under vacuum and the crude product waspurified using silica gel chromatography to yield the desired amideEC2258 (22 mg, 77%). [M+H]⁺=Calculated 906.29, found 906.47

EC2259: Disulfide EC2258 (15 mg, 0.017 mmol) and the folate spacerEC1579 (36.6 mg, 0.022 mmol) were dissolved in anhydrous DMSO underargon. DIPEA (18 μl, 0.1 mmol) was added to the reaction mixture andstirred for 2 hours. The crude product was purified by low pressurechromatography using C18 stationary phase and eluted with Ph7 buffer andacetonitrile, followed by lyophilization to produce conjugate EC2259(12.4 mg, 30%). [M+H]⁺=Calculated 2473.89, 1237.94, found 1238.19

EC2259 (7 mg, 2.83 μmol) was dissolved in DI H₂O (3 ml) with theaddition of conc. HCl (6 drops). The reaction was monitored untildeprotection was complete and the product purified by low pressurechromatography using C18 stationary phase and eluted with H₂O andacetonitrile, followed by lyophilization to yield the desired conjugateEC2288 (5.5 mg, 80%). [M+H]⁺=Calculated 2429.86, 1215.93, found 1215.88

Methyl vanillate (2.18 g, 11.98 mmol) and Ph₃P (4.71 g, 17.97 mmol) inTHF (20 mL) was cooled to 0° C. and to which was added DIAD (2.59 mL,13.18 mmol) dropwise. The reaction was stirred at 0° C. for 1 hr.1,5-petanediol (0.6 mL, 5.75 mmol) in THF (20 mL) was added over 30 min.The reaction was stirred overnight and prESIpitate formed and wascollected with filtration. The filtrate was concentrated to form moresolid. The solid was combined and triturated with MeOH (5 mL) to givequite clean product EC1624 1.74 g in yield of 70%. ¹H NMR (CDCl₃, δ inppm): 7.66 (m 2H), 7.62 (m, 2H), 6.87 (m, 2H), 4.10 (m, 4H), 3.89 (m,12H), 1.95 (m, 4H), 1.69 (m, 2H). ¹³C NMR: 166.88, 152.50, 148.86,132.12, 132.04, 131.88, 128.52, 128.42, 123.50, 122.55, 112.35, 111.46,68.67, 56.03, 51.93, 28.73, 22.52, 21.92.

EC1624 (201.2 mg, 0.465 mmol) in Ac₂O (1.2 mL) was cooled to 0° C. andthen Cu(NO₃)₂.3H₂O (280.3 mg, 1.16 mmol) was added slowly and after 1hr, the ice-bath was removed. The reaction was stirred at r.t. for 4hrs. The reaction was poured into ice water and stirred for 1 h tillyellow precipitate formed and was collected with filtration. The solidwas washed with more cold water (2 mL, 3×) and air-dried. 198.4 mg ofEC1686 was obtained in yield of 82%. LCMS: [M+NH₄]⁺ m/z=540.

EC1686 (198.4 mg) was dissolved in THF (2 mL) and treated with aq. NaOH(2 mL, 1 M) and heated to 400 C for 3 hrs. The solvent was removed invacuo. The aqueous phase was acidified to pH 1 with concentrated HCl toform precipitate, which was collected by filtration and was washed withH₂O (1 mL, 3×). The solid was air-dried to give the acid 187.7 mg ofEC1687 in quantitative yield. LCMS: [M+NH₄]⁺ m/z=512.

Acid EC1687 was dissolved in 0.5 M aq. NaOH (6 mL) and hydrogenation wascarried out with Pd/C (10%, 4.82 mg) under H₂ (45 PSI) in thehydrogenation parr. The reaction was shook for 5 hrs and the filteredthrough a pad of celite and the filtrate was adjusted to pH 2-3 withconcentrated HCl while stirring. The formed precipitate was isolated byfiltration and washed with H₂O (1 mL, 3×). The solid was dried in adesiccator with the presence of P₂O₅ under high vacuum overnight. EC1709was obtained 34.2 mg as a brown solid in the yield of 81%. LCMS: [M−H]⁻m/z=433.

(S)-1-tert-butyl 2-methyl 4-oxopyrrolidine-1,2-dicarboxylate wasconverted to EC1692 by Wittig reaction: Ph₃PCH₃Br (917.8 mg, 2.57 mmol)in THF (30 mL) was treated with KO^(t)Bu (1 M in THF, 2.57 μL, 2.57mmol) at 0° C. by dropwise addition. The reaction was kept at roomtemperature for 2 hrs. Into the stirred solution was added the ketone(250 mg, 1.028 mmol) in THF 20 mL) at 0-10° C. The reaction was thenstirred at room temperature for overnight. The reaction was quenchedwith H₂O/EtOAc (1:1, 40 mL) after most of the THF was removed in vacuo.The aq. phase was extracted with EtOAc (20 mL, 3×) and the organic phasewas washed with H₂O, followed by brine, and dried over anhydrous Na₂SO₄and concentrated. The residue was purified with CombiFlash in 0-50%EtOAc/p-ether to afford the EC1692 77.2 mg, in yield of 31%. LCMS:[M-Boc+H]⁺ m/z=142.

(S)-1-tert-butyl 2-methyl 4-methylenepyrrolidine-1,2-dicarboxylate(353.2 mg, 1.46 mmol) in DCM/toluene (1:3, 9.8 mL) was treated withDibal (1 M in toluene, 2 eq, 2.92 mmol) dropwise at −78° C. under argon.The reaction was stirred at −78° C. for ca. 4 hrs. Then the reaction wasquenched with addition of 60 μL of MeOH at −78° C. followed by 5% HCl(0.5 mL) and EtOAc (18 mL). The cold bath was removed and the reactionwas stirred for 30 min. The EtOAc layer was separated and washed withbrine, dried over anhydrous Na₂SO₄ and concentrated to give the crudealdehyde intermediate.

The crude aldehyde was redissolved in dry DCM (10 mL) and treated withethanolamine (106 μL, 1.75 mmol) in the presence of anhydrous MgSO₄ (5mmol, mg) at r.t. (room temperature) under Ar. The reaction was stirredfor 1 hr. Then into this reaction mixture was added FmocCl (755.4 mg,2.92 mmol) and TEA (611 μL, 4.38 mmol) and the reaction was stirred forovernight at r.t. under Ar. The reaction was purified with CombiFlash in0-50% EtOAc/petroleum ether to provide EC1768 334.2 mg, 46% for 3 steps.LCMS: [M+H]⁺ m/z=477. ¹H NMR (CD₃OD, δ in ppm): 7.81 (d, J=7.5 Hz, 2H),7.60 (d, J=7 Hz, 2H), 7.40 (m, 2H), 7.32 (m, 2H), 4.96 (br, 2H), 4.60(br, 1H), 4.23 (t, J=5.5 Hz, 1H), 3.97 (br, 2H), 3.73 (br, m, 3H), 2.50(br, 2H), 1.47 (s, 1H), 1.39 (s, 9H).

EC1768 was deprotected in TFA/DCM (1:1) at r.t. for 30 min, the solventwas removed in vacuo. The product (EC1769) was used for the couplingreaction with EC1709 without further purification. LCMS: [M+H]⁺ m/z=377.

EC1709 (42.0 mg, 0.097 mmol), EC1769 (0.053 mmol), and PyBOP (29.0 mg,0.056 mmol) were dissolved in DMF/DCM (0.5 mL/0.5 mL) and treated withDIPEA (74 μL, 0.43 mmol) at r.t. under Ar. The reaction was completedwithin 1 hr, then loaded onto CombiFlash column in 0-20% MeOH/DCM toafford the pure product EC1770 (25.5 mg, 60%). LCMS: [M+H]⁺ m/z=793. ¹HNMR (CD₃OD, δ in ppm):

EC1770 (25.5 mg, 0.032 mmol) was dissolved in DCM (1 mL) was treatedwith diethylamine (DEA, 83.5 μL, 0.80 mmol) at r.t. under Ar. Thereaction was stirred for 2 hrs, and then the solvent was removed invacuo. This immine was redissolved in DCM (0.3 mL) and absolute ethanol(0.6 mL) and cooled to 0° C. To this cooled solution was added NaBH₄(1.33 mg, 0.0352 mmol) and the reaction was stirred for 5 min at 0° C.then the ice bath was removed. The reaction was stirred at r.t. for 2hrs. After EtOH was removed, the reaction mixture was purified withCombiFlash in 0-15% MeOH/DCM to afford 9.9 mg of EC2170 (yield 60% for 2steps). LCMS: [M−H]⁻ m/z=510. ¹H NMR (CD₃OD, δ in ppm): 7.41 (s, 1H),7.31 (s, 1H), 6.32 (s, 1H), 6.26 (s, 1H), 5.07 (m, 2H), 4.27 (m, 2H),4.00 (q, J=7 Hz, 4H), 3.75 (s, 3H), 3.73 (s, 3H), 3.57 (dd, J=1.5, 13Hz, 1H), 2.98 (m, 1H), 2.49 (m, 1H), 1.88 (m, 4H), 1.68 (m, 2H).

EC1693 was synthesized by the same methods as EC1768. LCMS: [M+H]⁺m/z=468. ¹H NMR (CDCl₃, δ in ppm): 8.47 (d, J=5 Hz, 1H), 7.66 (m, 2H),7.09 (m, 1H), 5.16 (br, 1H), 4.97 (br, 2H), 4.38 (br, 3H), 4.05 (br,2H), 3.85 (br, 3H), 3.20 (m, 1H), 3.06 (br, 2H), 2.85 (br, 1H), 2.52 (m,1H), 1.55 (s, 3H), 1.43 (s, 9H).

EC2186 was synthesized by the same methods as EC1769. LCMS: [M+H]⁺m/z=368.

EC2181: Acid EC2170 (4.95 mg, 0.0097 mmol) was dissolved in dry DMF (0.5mL) and was treated with PyBOP (10.1 mg, 0.0194 mmol). To the reactionmixture was added the solution of EC2186 (0.01 mmol, from 4.76 mg ofEC1693) and DIPEA (30 μL, 0.17 mmol) in DCM (0.5 mL). The reaction wasstirred for 5 hrs and was purified with prep-HPLC in 10-100% MeCN/pH7buffer to give pure EC2181 2.3 mg (30% in yield). LCMS: [M+H]⁺ m/z=861.¹H NMR (CD₃OD, δ in ppm): 8.37 (s, 1H), 7.77 (m, 2H), 7.40 (s, 1H), 7.19(s, 1H), 6.42 (s, 1H), 6.26 (s, 1H), 5.07 (m, 4H), 5.01 (s, 1H), 4.56(d, J=1 Hz, 1H), 4.20 (m, 6H), 4.01 (m, 7H), 3.75 (s, 3H), 3.73 (s, 3H),3.67 (d, J=11 Hz, 2H), 3.44 (m, 4H), 3.13 (br, 2H), 3.05 (m, 1H), 2.50(3H), 2.48 (m, 2H), 1.85 (m, 3H) 1.26 (m, 4H).

EC1579 (8.7 mg, 0.0052 mmol) in DMSO (0.5 mL) under Ar was stirred to aclear solution the solution of EC2181 (3.7 mg, 0.0043 mmol) in DMSO (0.5mL) was added and followed by addition of TEA (3.6 μL, 0.026 mmol). Thereaction was stirred for 1 hr at r.t. under Ar. The product was isolatedwith prep-HPLC in 10-100% MeCN/pH 7 buffer to give EC2182 6.5 mg (62% inyield) as a solid after lyophilized. LCMS: [M+3H]³⁺ m/z=810. ¹H NMR (9:1DMSO-d6:D₂O, δ in ppm): 8.53 (s, 1H), 7.55 (d, J=8 Hz, 2H), 7.21 (s,1H), 6.60 (d, J=7.5 Hz, 3H), 6.29 (s, 1H), 6.22 (s, 1H), 4.97 (s, 2H),4.91 (s, 1H), 4.45 (s, 3H).

Methyl-4-Benzyloxy-3-methoxy Benzoate (5.00 g, 18.4 mmol) was dissolvedin Ac₂O (23.5 mL) and cooled to 0° C. Cu(NO₃)₂ (5.05 g, 27.0 mmol) wasadded in small portions over 10 minutes. After 90 min, LCMS indicatedproduct formation. The mixture was poured into ice-water and stirred for45 minutes. Crude product was recovered by centrifugation, rinsed withwater, and dried. The crude product was purified via silica-gelchromatography on a Combiflash system using a petroleum ether/ethylacetate gradient. 5.80 g (99%), off-white solid. ¹H NMR (CD₃OD, δ inppm): 7.62 (s, 1H), 7.45 (d, 2H), 7.40 (t, 2H), 7.35 (m, 1H), 7.25 (s,1H), 5.20 (s, 2H), 3.95 (s, 3H), 3.90 (s, 3H). MS (ESI-QMS): m/z=318.03(M+H).

EC2093 (5.80 g, 18.2 mmol) was dissolved in CH₂Cl₂ (10 mL). A mixture of2.5 mL CH₂Cl₂ and 2.5 mL of CH₃SO₂OH was added and the mixture stirred.After 3 hours, LCMS indicated product formation. The solvent was removedand the product was purified via silica-gel chromatography on aCombiflash system using a CH₂Cl₂/CH₃OH gradient to provide EC1882 3.46 g(84%), as off-white solid. ¹H NMR (CD₃OD, δ in ppm): 7.35 (s, 1H), 7.2(s, 1H), 3.95 (s, 3H), 3.90 (s, 3H). MS (ESI-QMS): m/z=225.78 (M−H).

EC1882 (1.0331 g, 4.55 mmol) was dissolved in ethanol (200 proof, 70mL). Pd/C (10%, 200 mg) was added. The reaction flask was evacuated andbackfilled with H₂ three times. H₂ was applied by balloon for 3 hours,at which point the flask was evacuated and backfilled with air threetimes. Celite was added and the product filtered through with ethanoland concentrated. Typical yield 781.0 mg, 90% recovery, brown solid. ¹HNMR (CD₃OD, δ in ppm): 7.25 (s, 1H), 6.20 (s, 1H), 3.85 (s, 3H), 3.80(s, 3H). MS (ESI): m/z=196.23 (M−H).

The phenol compound (2.2044 g, 12.1 mmol) was dissolved in acetone(dried through a pad of Na₂SO₄, 48.4 mL) and to this solution was added1,5-dibromopentane (49.4 mL, 36.3 mmol) and K₂CO₃ (6.69 g, 48.4 mmol).The reaction was heated to reflux under Ar for 6 hrs. The reaction wascooled to RT and the solid was filtered out. The filtrate wasconcentrated and purified with CombiFlash in 0-30% EtOAc/p-ether toobtained EC1851 (3.3893 g, yield 84.5%) as a solid. LCMS: [M+H]⁺m/z=331. ¹H NMR (CDCl₃, δ in ppm): 7.65 (dd, J=8.5, 2.0 Hz, 1H), 7.54(d, J=2.0 Hz, 1H), 6.86 (d, J=8.50 Hz, 1H), 4.08 (t, J=6.50 Hz, 2H),3.91 (s, 3H), 3.89 (s, 3H), 3.44 (t, J=6.5 Hz, 2H), 1.95 (m, 4H), 1.65(m, 2H).

EC1851 (3.3893 g, 10.23 mmol) in Ac₂O (52 mL) was cooled to 0° C. andtreated with Cu(NO₃).3H₂O (2.967 g, 12.28 mmol) by slow addition. Thereaction was stirred at 0° C. for 1 hr then at RT for 2 hrs. After thereaction was completed, the reaction mixture was poured into ice waterand stirred for 1 hr. The resultant precipitate was collected byfiltration. The product was washed with water (3×) and air-dried asEC1852 (3.7097 g, yield 96%). LCMS: [M+H]⁺ m/z=376. ¹H NMR (CDCl₃, δ inppm): 7.41 (s, 1H), 7.05 (s, 1H), 4.08 (t, J=6.50 Hz, 2H), 3.94 (s, 3H),3.89 (s, 3H), 3.42 (t, J=7.0 Hz, 2H), 1.93 (m, 4H), 1.63 (m, 2H).

The solution of EC1852 (37.6 mg, 0.1 mmol) and Hochest dye (53.3 mg, 0.1mmol) in DMF (1.5 mL) under Ar was treated with K₂CO₃ at rt. Thereaction was heated to 60° C. and kept for overnight. Then the reactionwas cooled to rt and the solid was filtered out. The residue waspurified with Prep-HPLC (Mobile phase A: 50 mM NH₄HCO₃ buffer, pH 7.0;B=ACN. Method: 10-100 B % in 30 min.) to afford EC1859 (13.1 mg, yield18%). LCMS: [M+H]⁺ m/z=720.71.

EC1859 (13.1 mg, 0.0182 mmol) was dissolved in THF/MeOH/H₂O (3/1/1, 0.2mL) and treated with aq. LiOH solution (1 M, 36 μL) for 4 hrs at rtunder Ar. Most of the solvent was removed in vacuo and the aqueous phasewas acidified with concentrated HCl to pH 2-3, the precipitate wascollected as solid (EC1863, 12.8 mg, without purification) byfiltration. The filtrate was washed with water (3×) and air dried forthe next step. LCMS: [M+H]⁺ m/z=706.

EC1863 (15.7 mg, 0.022 mmol) in MeOH (10 mL) was subjected tohydrogenation in a Parr shaker (10% wet Pd/C, 5% wt, 7.85 mg, H₂ 41 PSI)for 2 hrs. The product was isolated by filtration through a pad ofcelite. The solvent was removed in vacuo to give crude EC1870, LCMS:[M+H]⁺ m/z=676.79. The crude product in DMF (0.5 mL) was mixed with thesolution of EC2186 (8.81 mg, 0.024 mmol) in DCM (2.0 mL). The reactionmixture was treated with PyBOP (20.8 mg, 0.04 mmol) and DIPEA (13.9 uL,0.08 mmol) under Ar at rt. The reaction was stirred for overnight andthen purified with Prep-HPLC (Mobile phase A: 50 mM NH₄HCO₃ buffer, pH7.0; B=ACN. Method: 10-100 B % in 30 min.) to afford 17.4 mg EC1869 inthe yield of 85% for the two steps. LCMS: [M+H]⁺ m/z=1025.9. ¹H NMR(CD₃OD, δ in ppm, selected data): 8.36 (s, 1H), 8.25 (d, J=1.0 Hz, 1H),8.03 (m, 2H), 7.96 (m, 1H), 7.77 (m, 3H), 7.69 (d, J=8.5 Hz, 1H), 7.52(d, J=9.0 Hz, 1H), 7.16 (m, 2H), 7.06 (m, 4H), 6.43 (n, 1H).

EC1579 (10.24 mg, 0.006 mmol) was dissolved in DMSO (0.3 mL) and water(0.2 mL) and bubbled with Ar at rt in an amber vial. To this solutionwas added a solution of EC1869 (5.0 mg, 0.0049 mmol) in DMSO (0.2 mL)and followed by addition of DIPEA (5.1 μL, 0.029 mmol). The reaction wasstirred at rt under Ar for 30 min. The reaction was purified withprep-HPLC (10 to 100% ACN in 50 mM NH₄HCO₃, pH 7.4) to give theconjugate EC1879 (3.9 mg, 30% yield). LCMS: [M+2H]²⁺ m/z=1297, [M+3H]³⁺m/z=865.

To a solution of Val-Ala-OH (1 g, 5.31 mM) in water (40 ml) was addedNa₂CO₃ (1.42 g, 13.28 mM) and cooled to 0° C. before dioxane (40 mL) wasadded. A solution of Fmoc-Cl (1.44 g, 5.58 mM) in dioxane (40 mL) wasadded dropwise over 10 min at 0° C. The reaction mixture was stirred at0° C. for 2 h. Then the reaction mixture was allowed to stir at RT for16 h. Dioxane was removed under vacuum, the reaction mixture dilutedwith water (450 mL), pH was adjusted to 2 using 1N HCl and extractedwith EtOAc (3×250 mL). The combined organic layers were washed withbrine, dried over MgSO₄, filtered, concentrated under reduced pressureand dried to yield Fmoc-Val-Ala-OH. This product was suspended in dryDCM (25 ml), PABA (0.785 g, 6.38 mM) and EEDQ (1.971 g, 7.97 mM) wereadded. The resulting mixture was treated under Argon with methanol untila clear solution was obtained. The reaction was stirred overnight andfiltered. The filtrate was washed with diethyl ether (4×) and driedunder high vacuum to yield EC1930 (1.85 g, 68%). ¹H NMR (500 MHz,CD₃OD): δ 7.79 (d, J₁=8.0 Hz, 2H), 7.65 (t, J₁=7.0 Hz, J₂=7.5 Hz, 2H),7.54 (d, J₁=8.0 Hz, 2H), 7.38 (t, J₁=7.5 Hz, J₂=7.5 Hz, 2H), 7.33-7.24(m, 4H), 4.54 (s, 2H), 4.48 (q, J₁=14.0 Hz, J₂=7.0 Hz, 1H), 4.42-4.32(m, 2H), 4.22 (t, J₁=7.0 Hz, J₂=6.5 Hz, 1H), 3.94 (d, J₁=7.0 Hz, 1H),2.07 (m, 1H), 1.43 (d, J₁=7.5 Hz, 3H), 0.97 (d, J₁=7.0 Hz, 3H), 0.95 (d,J₁=7.0 Hz, 3H); LCMS (ESI): (M+H)⁺=Calculated for C₃₀H₃₃N₃O₅, 516.24;found 516.24

To a mixture of 1-(tert-butyl) 2-methyl(S)-4-methylenepyrrolidine-1,2-dicarboxylate (0.5 g, 2.07 mmol) in THF(10 mL) was added LiBH₄ (67.7 mg, 3.11 mmol) in portions at 0° C. underargon. The mixture was allowed to warm to room temperature over 2.5hours. It was cooled to 0° C. and quenched with H₂O. The mixture wasextracted with EtOAc (3×30 mL) and the organic phase was washed withH₂O, brine sequentially and dried over anhydrous MgSO₄. It was filteredand concentrated in vacuo. The crude product EC2404 was used in nextstep without further purification.

To a mixture of EC2404 and pyridine (0.84 ml, 10.35 mmol) indichloromethane (8 ml) was added Dess-Martin periodinane (1.2 g, 2.90mmol) at 0° C. It was stirred at room temperature for 2 hours. The crudeproduct was purified with CombiFlash in 0-40% EtOAc/p-ether to afford0.26 g of EC2405 in 59.3% yield. ¹H NMR (500 MHz, CDCl₃) (rotamers): δ9.56 and 9.49 (s, 1H), 5.03 (m, 2H), 4.35-4.20 (m, 1H), 4.13-4.02 (m,2H), 2.86-2.71 (m, 1H), 2.67-2.64 (m, 1H), 1.49 and 1.44 (s, 9H).

A mixture of EC2405 (42.7 mg, 0.20 mmol), 2-aminoethane-1-ol (12.8 □l,0.21 mmol) and molecular sieves in toluene (1 ml) was stirred at roomtemperature for 1.5 hours to generate the tert-butyl(2S)-4-methylene-2-(oxazolidin-2-yl)pyrrolidine- 1-carboxylate in situ.

The proline derived aldehyde (550 mg, 2.6 mmol) was dissolved in DCM (10mL), MgSO₄ (3 g) was added followed by dropwise addition of ethanolamine(0.16 mL, 2.6 mmol) in DCM (10 mL) and was added to the EC2405 mixture.The reaction was stirred at rt for 1 hr. Filtration and concentrationunder vacuum gave the oxazoline intermediate. In another flask, EC1930(516 mg, 1.0 mmol) was dissolved in THF (40 mL) and pyridine was added(0.8 mL, 10 mmol). The solution was cooled to −78° C., and diphosgene(0.16 mL, 1.5 mmol) was added. The reaction was stirred at −78° C. for 1h, DCM (20 mL) and a solution of oxazolidine intermediate was addeddropwise. The reaction mixture was allowed to warm to −20° C. overseveral hours. LC-MS and TLC showed product formation. The reactionmixture was concentrated with silica gel and purified by flashchromatography (120 gold Redisep column, 0-100% EtOAc in petroleumether) to give EC2076 (0.59 g, 74%). LCMS (ESI): (M+H)⁺=Calculated forC₄₄H₅₃N₅O₉, 796.38; found 796.74.

EC2076 (101.0 mg, 0.127 mmol) was stirred in TFA/DCM (0.5 mL each) at rtfor 30 min. LC-MS showed complete removal of Boc group. The reactionmixture was concentrated under high vacuum to remove TFA and DCM,re-dissolved in DMF (1.0 mL), and adjusted pH to 8-9 by adding Hunig'sbase (0.3 mL). EC1870 (86.0 mg, 0.127 mmol) was added, followed by PyBoP(84 mg, 0.16 mmol) and the reaction was stirred at rt for 2 h. LC-MS at90 min showed that the major peak had the desired product. The reactionmixture was loaded onto a silica gel cartridge and purified by flashchromatography (12 g gold, 0-30% MeOH/DCM) to give desired product,EC2078 (140 mg, 81%). LCMS (ESI): (M+H)⁺=Calculated for C₇₇H₈₄N₁₂O₁₁,1353.64; found 1354.18.

EC2078 (140 mg, 0.10 mmol) was dissolved in DEA/DCM (12/18 mL) andstirred at rt for 30 min. LC-MS showed complete removal of Fmoc group.The reaction mixture was concentrated under high vacuum to remove excessdiethylamine and re-dissolved in DCM (5 mL). MP-tetra-EG-Osu (62 mg,0.12 mmol) was added and the reaction was stirred at rt for 1 hr. Thereaction mixture was concentrated, redissolved in DMSO and loadeddirectly to HPLC column and purified by preparative HPLC (C18 column,5-80% ACN/pH7 buffer) giving desired product EC2079 (55.8 mg, 36%).LCMS: [M+2H]²⁺ m/z=Calculated for C₈₀H₁₀₀N₁₄O₁₇, 765.37; found 765.74.

EC1579 (9.85 mg, 0.006 mmol) was stirred in DMSO (2 mL) until dissolved.DIPEA (50 uL) was added, followed by EC2079 (6.24 mg, 0.004 mmol) inDMSO (2 mL). The reaction was stirred at RT for 50 min. LC-MS analysisat 10 min showed complete conversion. The reaction mixture was directlyloaded on a prep-HPLC column and purified (10-100% MeCN/Ammoniumbicarbonate, pH 7 buffer) to give desired product EC2080 (5.5 mg, 42%).¹H NMR (500 MHz, DMSO-D₆+D₂O) (selected data): δ 8.60 (s, 1H), 8.44-8.08(m*, 1H), 8.07 (d, J=8.5 Hz, 2H), 8.06-7.84 (m*, 2H), 7.80-7.57 (m*,2H), 7.57 (d, J=8 Hz, 2H), 7.51 (d, J=6.5 Hz, 2H), 7.44 (m*, 1H), 7.22(m*, 2H), 7.08 (d, J=8 Hz, 2H), 6.93 (d, J=8.5 Hz, 1H), 6.60 (d, J=8.5Hz, 2H), 6.33 (s, 1H), 4.95 (m*, 4H), 4.45 (m*, 3H); LCMS: [M+4H]⁴⁺m/z=Calculated for C₁₄₅H₁₉₈N₃₀O₅₁S, 803.34; found 803.80. * Due todiasteromeric and/or rotameric nature of the compound

EC2234 was synthesized in 91% yield following the procedure described inMurray et al. WO2008098368 ¹H NMR (500 MHz, CDCl₃) (rotamers): δ 6-5.8(m, 1H), 5.4-5.1 (m, 2H), 4.6-4.4 (m, 4H), 3.8-3.5 (m, 2H), 2.4-2 (m,2H).

To a mixture of EC2234 (1 g, 4.36 mmol) and imidazole (0.59 g, 8.72mmol) in DMF was added tert-Butyldiphenylchlorosilane (1.36 ml, 5.23mmol) dropwise at room temperature. The mixture was stirred at roomtemperature overnight. The reaction was quenched with water, extractedwith EtOAc (3×30 ml) and the organic phase was washed with H₂O, brinesequentially and dried over anhydrous MgSO₄ and concentrated. Theresidue was purified with CombiFlash in 0-80% EtOAc/p-ether to affordthe EC2235 1.84 g, in yield of 90%. ¹H NMR (500 MHz, CDCl₃): δ 7.68-7.60(m, 4H), 7.48-7.36 (m, 6H), 5.91 (m, 1H), 5.25 (m, 2H), 4.59 (m, 2H),4.43 (m, 1H), 4.24-3.60 (m, 4H), 3.53 (m, 2H), 1.05 (m, 9H). LCMS:[M+H]⁺ m/z=468.41.

To a mixture of EC2235 (0.94 g, 2.01 mmol) in THF (15 ml) was addedLiBH₄ (65.7 mg, 3.02 mmol) in portions at 0° C. under argon. The mixturewas allowed to warm to room temperature over 2.5 hours. It was cooled to0° C. and quenched with H₂O. The mixture was extracted with EtOAc (3×30ml) and the organic phase was washed with H₂O, brine sequentially anddried over anhydrous MgSO₄. It was filtered and concentrated in vacuo.The crude product was used in next step without further purification.0.88 g of EC2236 was obtained in 99% yield. ¹H NMR (500 MHz, CDCl₃): δ7.68-7.60 (m, 4H), 7.48-7.36 (m, 6H), 5.91 (m, 1H), 5.25 (m, 2H), 4.59(m, 2H), 4.43 (m, 1H), 4.24-3.60 (m, 4H), 3.53 (m, 2H), 1.05 (m, 9H).LCMS: [M+H]⁺ m/z=440.41.

To a mixture of EC2236 (0.88 g, 2.0 mmol) in DCM (6 ml) was addedDess-Martin reagent (1.02 g, 2.4 mmol) at room temperature. The mixturewas stirred at room temperature for 4 hours. The crude product waspurified with CombiFlash in 0-40% EtOAc/p-ether to afford 0.69 g ofEC2237 in 80% yield. ¹H NMR (500 MHz, CDCl₃): δ 9.46 (d, J=48 Hz, 1H),7.64-7.59 (m, 4H), 7.46-7.26 (m, 6H), 5.90 (m, 1H), 5.30 (d, J=11 Hz,1H), 5.22 (m, 1H), 4.62 (m, 2H), 4.38 (m, 2H), 3.62 (dd, J₁=11 Hz,J₂=62.5 Hz, 1H), 3.44 (m, 2H), 2.10 (M, 1H), 1.82 (M, 2H), 1.05 (s, 9H).LCMS: [M+H]⁺ m/z=438.35.

To a mixture of EC2237 (0.395 g, 0.9 mmol) in ethanol (5 ml) andTriethyl orthoformate (0.6 ml, 3.6 mmol) was added p-TsOH (catalyticamount) at room temperature. The mixture was stirred at room temperaturefor 3 hours. The crude product was purified with CombiFlash in 0-40%EtOAc/p-ether to afford 0.45 g of EC2238 in 97% yield. ¹H NMR (500 MHz,CDCl₃): δ 7.63 (m, 4H), 7.37 (m, 6H), 5.93 (m, 1H), 5.30-5.19 (m, 2H),4.77-4.49 (m, 4H), 4.11 (m, 1H), 3.67 (m, 2H), 3.54-3.42 (m, 2H),3.37-3.23 (m, 2H), 2.22 (m, 1H), 1.98 (m, 1H), 1.19 (m, 3H), 1.04 (s,9H), 0.98 (m, 3H). LCMS: [M+H]⁺ m/z=512.58.

To a mixture of EC2238 (0.446 g, 0.87 mmol) in THF (6 ml) was added TBAFsolution (1.05 ml g, 1.05 mmol) at room temperature under argon. Themixture was stirred at room temperature overnight. The crude product waspurified with CombiFlash in 0-40% EtOAc/p-ether to afford 0.23 g ofEC2239 in 95% yield. ¹H NMR (500 MHz, CDCl₃): δ 5.95 (m, 1H), 5.31 (d,J=17.5 Hz, 1H), 5.21 (d, J=10.5 Hz, 1H), 4.87 (s, 1H), 4.60 (m, 3H),4.13 (m, 1H), 3.74 (m, 2H), 3.53 (m, 5H), 2.41 (m, 1H), 1.89 (m, 1H),1.21 (t, J₁=_(J)=7.5 Hz, 3H) 1.16 (t, J₁=_(J)=7.5 Hz, 3H). To a mixtureof DMSO (0.32 g, 4.51 mmol) in DCM (10 ml) was added oxalyl chloride(1.13 ml, 2 M in methylene chloride, 2.25 mmol) at −78° C. under argon.After stirring for 30 minutes, EC2239 (0.56 g, 2.05 mmol) was added at−78° C. The mixture was stirred at −78° C. for 2 hours, then it wastreated with Et₃N (1.42 ml, 10.25 mmol). It was allowed to warm to roomtemperature. The reaction mixture was diluted with DCM and quenched withbrine. It was washed with brine and dried over anhydrous MgSO₄. Thecrude product was purified with CombiFlash in 0-40% EtOAc/p-ether toafford 0.43 g of EC2242 in 77% yield. ¹H NMR (500 MHz, CDCl₃): δ 5.95(m, 1H), 5.35-5.22 (m, 2H), 4.70-4.58 (m, 3H), 4.40 (dd, J₁=9.5 Hz,J₂=31.5 Hz, 1H), 3.89 (m, 1H), 3.77 (m, 3H), 3.54 (m, 1H), 3.46 (m, 1H),2.72 (d, J=18.5 Hz, 1H), 2.48 (m, 1H), 1.23 (t, J=J₂=7.5 Hz, 3H) 1.13(t, J=J₂=7.5 Hz, 3H).

Potassium tert-butoxide (2.54 ml, 1M in THF, 2.54 mmol) was addeddropwise to a suspension of methyltriphenylphosphonium bromide (0.91 g,2.54 mmol) in THF (10 ml) at 0° C. under argon. After being stirred for2 hours at 0° C., a solution of EC2242 (0.345 g, 1.27 mmol) g in THF (8ml) was added dropwise, and the reaction was allowed to warm to roomtemperature. After being stirred overnight the reaction mixture wasdiluted with EtOAc and washed with H₂O, brine sequentially and driedover anhydrous MgSO₄. It was filtered and concentrated in vacuo. Thecrude product was purified with CombiFlash in 0-20% EtOAc/p-ether toafford 0.306 g of EC2246 in 89.5% yield. ¹H NMR (500 MHz, CDCl₃): δ 5.94(5.94, m, 1H), 5.31 (d, J=17.5 Hz, 1H), 5.20 (d, J=11 Hz, 1H), 4.91 (m,2H), 4.71 (m, 3H), 4.14 (m, 2H), 3.94 (d, J=15 Hz, 1H), 3.72 (M, 2H),3.48 (m, 2H), 2.79 (d, J=16.5 Hz, 1H), 2.60 (m, 1H), 1.20 (t, J₁=J₂=7.5Hz, 3H), 1.14 (t, J₁=J₂=7.5 Hz, 3H).

A mixture of EC2246 (43.3 mg, 0.16 mmol), thionyl chloride (2.34 ml,0.032 mmol) and acetyl chloride (18.4 ml, 0.26 mmol) was stirred at 70°C. for 2 h. It was cooled to room temperature and concentrated underreduced pressure. The crude chloro hemi-acetal was used for next stepwithout further purification.

A mixture of methyl 3-(1H-imidazol-4-yl)propanoate (29.6 mg, 0.19 mmol)and sodium hydride (7.04 mg, 60% dispersion in mineral oil, 0.18 mmol)in DMSO was stirred at room temperature for 30 minutes. It wastransferred in to a flask containing the chloro hemi-acetal and themixture was stirred at room temperature overnight. The crude product waspurified with CombiFlash in 0-100% EtOAc/p-ether to afford 23.1 mg ofEC2247 in 38.3% yield. ¹H NMR (500 MHz, CDCl₃) (Diastereomers): δ 7.55(m, 1H), 7.36 (s, 1H), 6.77 (s, 1H), 6.64 (s, 1H), 5.92, (m, 2H),5.34-5.19 (m, 2H), 5.03 (m, 2H), 4.90-4.75 (m, 2H), 4.63-4.52 (m, 4H),4.40 (m, 2H), 4.22 (m, 2H), 3.932 (m, 2H), 3.67 (s, 6H), 3.56-3.41 (m,6H), 3.39-2.85 (m, 4H), 2.76 (m, 2H), 2.72-2.63 (m, 6H), 1.21-1.14 (m,6H). LCMS: [M+H]⁺ m/z=378.68.

A mixture of EC2247 (42 mg, 0.11 mmol), Pyrrolidine (10.2 μL, 0.12 mmol)and Pd(PPh₃)₄ (6.4 mg, 0.0055 mmol) in DCM (0.6 ml) was stirred at roomtemperature for 3 hours. It was diluted with DCM, washed with H₂O, brinesequentially and dried over anhydrous MgSO₄. It was filtered andconcentrated in vacuo. The crude product was used for next step withoutfurther purification. LCMS: [M+H]⁺ m/z=294.60.

A mixture of EC2248 (10.72 mg, 0.037 mmol), EC1870 (24.7 mg, 0.037mmol), PyBop (28.9 mg, 0.056 mmol) and DIEA (19.4 μl, 0.11 mmol) in DMSO(1 ml) was stirred at room temperature overnight. The crude product waspurified with prep-HPLC (10 to 100% acetonitrile in 20 mM NH₄HCO₃, pH7.4) to yield pure EC2224 (14.4 mg, 41%). LCMS: [M+H]⁺ m/z=952.15.

To a mixture of EC2224 (16 mg, 0.017 mmol) in THF (1.5 ml), MeOH (0.5ml) and H₂O (0.5 ml) was added LiOH (85 μl, 1.0 M solution, 0.085 mmol)at room temperature. The mixture was stirred at room temperature for 4hours. The solvent was removed under reduced pressure and the crudeproduct was used for next step without further purification. LCMS:[M+H]⁺ m/z=938.58.

A mixture of EC2250 (12.5 mg, 0.013 mmol),1-(2-aminoethyl)-1H-pyrrole-2,5-dione TFA salt (3.4 mg, 0.013 mmol),PyBop (10.4 mg, 0.02 mmol) and DIEA (6.8 μl, 0.04 mmol) in DMSO (1 ml)was stirred at room temperature for 1 hour. Then an aqueous solution ofEC1579 was added at room temperature. To the mixture was added EC1579(32.8 mg, 0.02 mmol) in H₂O (0.5 ml) The mixture was stirred at roomtemperature for 30 minutes and the crude product was purified withprep-HPLC (10 to 100% acetonitrile in 20 mM NH₄HCO₃, pH 7.4) to yieldpure EC2290 (2 mg, 5.6%). LCMS: [M+2H]²⁺ m/z=1370.76.

To a mixture of 1-(tert-butyl) 2-methyl(S)-4-methylenepyrrolidine-1,2-dicarboxylate (0.5 g, 2.07 mmol) in THF(10 mL) was added LiBH₄ (67.7 mg, 3.11 mmol) in portions at 0° C. underargon. The mixture was allowed to warm to room temperature over 2.5hours. It was cooled to 0° C. and quenched with H2O. The mixture wasextracted with EtOAc (3×30 mL) and the organic phase was washed withH2O, brine sequentially and dried over anhydrous MgSO₄. It was filteredand concentrated in vacuo. The crude product EC2404 was used in nextstep without further purification.

To a mixture of EC2404 and pyridine (0.84 ml, 10.35 mmol) indichloromethane (8 ml) was added Dess-Martin periodinane (1.2 g, 2.90mmol) at 0° C. It was stirred at room temperature for 2 hours. The crudeproduct was purified with CombiFlash in 0-40% EtOAc/p-ether to afford0.26 g of EC2405 in 59.3% yield. ¹H NMR (500 MHz, CDCl₃) (rotamers): δ9.56 and 9.49 (s, 1H), 5.03 (m, 2H), 4.35-4.20 (m, 1H), 4.13-4.02 (m,2H), 2.86-2.71 (m, 1H), 2.67-2.64 (m, 1H), 1.49 and 1.44 (s, 9H).

A mixture of EC2405 (42.7 mg, 0.20 mmol), 2-aminoethane-1-ol (12.8 0.21mmol) and molecular sieves in toluene (1 ml) was stirred at roomtemperature for 1.5 hours to generate the tert-butyl(2S)-4-methylene-2-(oxazolidin-2-yl)pyrrolidine-1-carboxylate in situ. Amixture of Fmoc-Val-Cit-OH (0.11 g, 0.22 mmol) and HATU (0.12 g, 0.30mmol) in DMF (2 ml) was stirred at room temperature for 1 hour, thenDIEA (0.11 ml, 0.61 mmol) was added. The tert-butyl(2S)-4-methylene-2-(oxazolidin-2-yl)pyrrolidine-1-carboxylate reactionmixture was transferred into this reaction mixture and stirred at roomtemperature overnight. The crude product was purified with CombiFlash in0-20% MeOH/DCM to afford 40 mg of EC2369 in 24.8% yield. LCMS: [M+H]⁺m/z=733.73.

A mixture of EC2369 (40 mg, 0.055 mmol) in 50% TFA/DCM (1 ml) solutionwas stirred at room temperature for 3 hours. It was concentrated invacuo to give the EC2370 as pale yellow solid. It was used in next stepwithout further purification. LCMS: [M+H]⁺ m/z=633.62.

A mixture of EC2370 (20 mg, 0.032 mmol) EC1870 (21.4 mg, 0.032 mmol),PyBop (24.7 mg, 0.047 mmol) and DIEA (16.6 μl, 0.095 mmol) in DMSO (1ml) was stirred at room temperature for 5 hours. The crude product waspurified with Combiflash in 0-20% MeOH/DCM to afford 10 mg of EC2371 in24.5% yield. LCMS: [M+H]⁺ m/z=1291.92.

To a mixture of EC2371 (10 mg, 0.008 mmol) in acetonitrile (1 ml) wasadded Et₂NH (12 μl, 0.116 mmol) at room temperature. The mixture wasstirred at room temperature for 4 hours. It was concentrated underreduced pressure. The crude product of EC2372 was used in next stepwithout further purification. [M+H]⁺ m/z=1069.29.

A mixture of EC2372 (0.008 mmol), Mal-PEG4-NHS (4.1 mg, 0.008 mmol) andDIEA (4.2 μl, 0.024 mmol) in acetonitrile (1 ml) was stirred at roomtemperature overnight. The reaction mixture was concentrated underreduced pressure and the crude product was purified by prep-HPLC (10 to100% acetonitrile in 20 mM NH₄HCO₃, pH 7.4) to yield pure EC2373. LCMS:[M+H]⁺ m/z=1467.99.

A mixture of EC2373 (46.4 mg, 0.032 mmol) and EC2045 (34.5 mg, 0.032mmol) in MeOH (0.5 ml) and DMSO (0.5 ml) was stirred at room temperatureovernight. The crude product was purified by prep-HPLC (10 to 100%acetonitrile in 20 mM NH₄HCO₃, pH 7.4) to yield pure EC2374. LCMS:[M+2H]²⁺ m/z=1280.63.

A mixture of EC2374 (41 mg, 0.016 mmol) and EMCH (5.4 mg, 0.016 mmol) inMeOH (0.5 ml) and DMSO (0.5 ml) was stirred at room temperatureovernight. The crude product was purified by prep-HPLC (10 to 100%acetonitrile in 20 mM NH₄HCO₃, pH 7.4) to yield pure EC2375. LCMS:[M+2H]²⁺ m/z=1384.71. ¹H NMR (500 MHz, DMSO): δ 8.59 (m, 1H), 8.12 (m,2H), 7.96 (M, 1H), 7.67-7.50 (m, 5H), 7.45 (m, 1H), 7.41-7.18 (m, 3H),7.17-7.06 (m, 3H), 6.98-6.84 (m, 4H), 6.76-6.58 (m, 3H), 6.40-6.30 (m,1H), 5.0-4.8 (m, 2H), 4.20-3.98 (m, 4H), 3.96-3.72 (m, 4H), 3.70-3.60(m, 6H), 3.2-3.0 (m, 7H), 2.91 (m, 1H), 2.85 (m, 1H), 2.61-2.65 (m, 4H),2.43 (m, 3H), 2.34-2.18 (m, 12H), 2.18-2.0 (m, 3H), 1.98-1.84 (m, 5H),1.79 (m, 6H), 1.72 (m, 10H), 1.64-1.36 (m, 15H), 1.3-1.02 (m, 18H),0.88-0.62 (m, 12H).

Boc-Py-Py-OMe (EC2155): To a solution of 500 mg HCl.H-Py-OMe (2.63mmol., 1.1 equiv), 573 mg Boc-Py-OH (2.38 mmol., 1.0 equiv), and 850 μLDIPEA (4.77 mmol., 2.0 equiv) in 5.4 mL DMF (0.44M) was added 1.24 gPyBOP (2.38 mmol., 1.0 equiv). The reaction mixture was stirred for 4 hat room temperature, and then diluted (15×) with deionized water. Theprecipitate that was isolated by centrifugation (4000 rpm for 10 min)and the supernatant was decanted yielding a pellet. The pellet wasresuspended in deionized water and sonicated for 5 min, before theprecipitate was recollected by centrifugation (repeated twice). Residualwater was removed by freezing and lyophilizing from the sample todryness. 853 mg (86.4%) of product was collected as a light brown solid.¹H NMR (CDCl₃): δ 7.45 (s, 1H), 7.39 (s, 1H), 6.83 (s, 1H), 6.72 (s,1H), 6.56 (s, 1H), 6.22 (s, 1H), 3.90 (s, 6H), 3.81 (s, 3H), 1.50 (s,9H). LC/MS (ESI): m/z=377.13 (M+H).

HCl*H-Py-Py-OMe (EC2156): 38 μl (0.03M) of 2N anhydrous hydrochloricacid (HCl) in diethyl ether was added to 424 mg of EC2155 (1.13 mmol.)and stirred for 5 h at room temperature. The reaction mixture was thendiluted with one volume of diethyl ether and filtered by a fritted glassfunnel. The filter cake was rinsed with excess diethyl ether (5×reaction volume), and dried in vacuo to yield 343 mg (97.5%) of theproduct as a tan solid. ¹H NMR (d6-DMSO): δ 10.07 (s, 1H), 9.97 (br s,3H), 7.46 (d, J=2.0 Hz, 1H), 7.10 (d, J=2.0 Hz, 1H), 6.98 (d, J=2.0 Hz,1H), 6.89 (d, J=2.0 Hz, 1H), 3.87 (s, 3H), 3.83 (s, 3H), 3.72 (s, 3H).LC/MS (ESI): m/z=277.07 (M+H).

Boc-Py-Py-Py-OMe (EC2157): EC2157 was synthesized accord to the sameproduced as EC2155. 832 mg of EC2156 yielded 1.19 g of EC2157 as a lightbrown solid in 89.7% yield. 1H NMR (d6-DMSO): δ 9.89 (s, 1H), 9.84 (s,1H), 9.07 (s, 1H), 7.45 (d, J=2.0 Hz, 1H), 7.20 (d, J=1.7 Hz, 1H), 7.04(d, J=1.5 Hz, 1H), 6.89 (m, 2H), 6.82 (s, 1H), 3.82 (s, 6H), 3.79 (s,3H), 3.72 (s, 3H), 1.44 (s, 9H). LC/MS (ESI): m/z=499.46 (M+H)HCl*H-Py-Py-Py-OMe (EC2158): EC2158 was synthesized accord to the sameproduced as EC2156. 541 mg of EC2157 yielded 343 mg of EC2158 as a tansolid in 92.1% yield. ¹H NMR (d6-DMSO): δ 10.08 (s, 1H), 10.03 (br s,3H), 9.93 (s, 1H), 7.44 (d, J=1.9 Hz, 1H), 7.23 (d, J=1.9 Hz, 1H), 7.09(d, J=2.0 Hz, 1H), 7.05 (d, J=1.5 Hz, 1H), 6.99 (d, J=1.9 Hz, 1H), 6.89(d, J=1.9 Hz, 1H), 3.88 (s, 3H), 3.83 (s, 3H), 3.82 (s, 3H), 3.72 (s,3H). LC/MS (ESI): m/z=402.44 (M+H).

Boc-Py-Py-Py-Py-OMe (EC2159): EC2159 was synthesized accord to the sameproduced as EC2155. 200 mg of EC2158 yielded 267 mg of EC2159 as a lightbrown solid in 93.6% yield. ¹H-NMR (d6-DMSO): δ 9.92 (s, 2H), 9.85 (s,1H), 9.07 (s, 1H), 7.46 (d, J=2.0 Hz, 1H), 7.22 (d, J=2.0 Hz, 1H), 7.21(d, J=1.4 Hz, 1H), 7.06 (d, J=1.9 Hz, 1H), 7.04 (d, J=1.5 Hz, 1H), 6.90(d, J=1.9 Hz, 1H), 6.88 (s, 1H), 6.83 (s, 1H), 3.85 (s, 6H), 3.84 (s,3H), 3.83 (s, 3H), 3.83 (s, 3H), 3.80 (s, 3H), 3.73 (s, 3H), 1.45 (s,9H). LC/MS (ESI): m/z=621.78 (M+H).

Boc-Py-Py-Py-OH (EC2161): 316 mg (0.643 mmol.) of EC2157 was added to asolution of 12.5 mL 1,4-dioxane and 12.5 mL 1 N aqueous sodium hydroxide(0.025M). The reaction mixture was stirred for 4 h at room temperaturebefore evaporating to dryness. The solid was dissolved in water,acidified to pH 3 with aqueous HCl, and extracted with ethyl acetate(3×). The combined organic layers were dried with sodium sulfate andconcentrated to yield 290 mg of a brown/orange solid (93.1%). ¹H NMR(CDCl₃) δ 7.41 (s, 1H), 7.21 (2, 2H), 6.82 (d, J=2.0 Hz, 2H), 6.74 (s,1H), 3.89 (s, 3H), 3.86 (s, 3H), 3.85 (s, 3H), 1.48 (s, 9H). LC/MS(ESI): m/z=485.49 (M+H).

Boc-Py-Py-Py-NH(CH₂)₃N(CH₃)₂ (EC2162): To a solution of 170 mg of EC2161(0.351 mmol., 1.0 equiv), 53.0 μl of 3-(dimethylamino)-1-propylamine(0.421 mmol., 1.2 equiv), and 125 □l of DIPEA (0.702 mmol., 2.0 equiv)in 3.5 ml of DMF (0.1M) was added 201 mg of PyBOP (0.386 mmol., 1.1equiv). The reaction mixture was stirred for 4 h at room temperature,before it was concentrated in vacuo to yield a dark brown oil. The crudeproduct was further purified via silica chromatography (0-10% methanolin DCM) to yield 147 mg the product as a white solid (73.6%). ¹H NMR(d6-DMSO): δ 9.87 (s, 1H), 9.83 (s, 1H), 9.06 (s, 1H), 8.13 (t, J=1.2Hz, 1H), 7.18 (d, J=0.3 Hz, 1H), 7.15 (d, J=1.9 Hz, 1H), 7.04 (d, J=1.5Hz, 1H), 6.92 (d, J=1.5 Hz, 1H), 6.87 (s, 1H), 6.82 (s, 1H), 3.82 (s,3H), 3.80 (s, 3H), 3.79 (s, 3H), 3.22 (t, J=6.1 Hz, 2H), 3.15 (d, J=2.4Hz, 2H), 2.77 (s, 6H), 1.82 (m, 2H), 1.44 (s, 9H). LC/MS (ESI):m/z=569.67 (M+H). 2HCl*H-Py-Py-Py-NH(CH₂)₃N(CH₃)₂ (EC2163): EC2163 wassynthesized accord to the same produced as EC2156. 110 mg of EC2162yield 99 mg of EC2163 as a pale brown solid in 98% yield. ¹H NMR(d6-DMSO): δ 10.05 (s, 1H), 9.91 (m, 4H), 9.89 (br s, 1H), 8.16 (t,J=1.2 Hz, 1H), 7.22 (d, J=1.4 Hz, 1H), 7.15 (d, J=1.9 Hz, 1H), 7.10 (d,J=1.9 Hz, 1H), 7.05 (d, J=1.5 Hz, 1H), 6.97 (d, J=1.9 Hz, 1H), 6.92 (d,J=1.5 Hz, 1H), 3.88 (s, 3H), 3.83 (s, 3H), 3.79 (s, 3H), 3.23 (m, 2H),3.04 (m, 2H), 2.75 (s, 3H), 2.74 (s, 3H), 1.82 (m, 2H). LC/MS (ESI):m/z=469.43 (M+H).

Boc-Py-Py-Py-Py-OH (EC2164): EC2164 was synthesized accord to the sameproduced as EC2161. 359 mg of EC2159 yielded 340 mg of EC2164 as abrown/orange solid in 97.0% yield. ¹H NMR (d6-DMSO): δ 9.98 (s, 1H),9.84 (s, 1H), 9.74 (s, 1H), 9.07 (s, 1H), 7.21 (s, 2H), 7.17 (s, 1H),7.03 (d, J=1.5 Hz, 1H), 7.00 (s, 1H), 6.87 (s, 1H), 6.82 (s, 1H), 3.83(s, 3H), 3.82 (s, 3H), 3.81 (s, 3H), 3.79 (s, 3H), 1.44 (s, 9H). LC/MS(ESI): m/z=607.72 (M+H).

Boc-Py-Py-Py-Py-NH(CH₂)₃N(CH₃)₂ (EC2165): EC2165 was synthesized accordto the same produced as EC2162. 335 mg of EC2164 yielded 240 mg ofEC2165 as a white solid in 62.9% yield. ¹H NMR (d6-DMSO): δ 9.90 (s,1H), 9.86 (s, 1H), 9.84 (s, 1H), 9.07 (s, 1H), 8.05 (t, J=5.7 Hz, 1H),7.22 (d, J=2.5 Hz, 1H), 7.20 (d, J=1.4 Hz), 7.17 (d, J=2.0 Hz, 1H), 7.04(d, J=1.5 Hz, 1H), 7.03 (d, J=1.9 Hz), 6.87 (s, 1H), 6.82 (s, 1H), 6.81(s, 1H), 3.83 (s, 6H), 3.79 (s, 3H), 3.78 (s, 3H), 3.22 (m, 2H), 2.22(t, J=7.2 Hz, 2H), 2.12 (s, 6H), 1.60 (m, 2H), 1.44 (s, 9H). LC/MS(ESI): m/z=691.56 (M+H).

2HCl*H-Py-Py-Py-Py-NH(CH₂)₃N(CH₃)₂ (EC2166): EC2166 was synthesizedaccord to the same produced as EC2156. 115 mg of EC2165 yielded 92 mg ofEC2166 as a pale brown solid in 92% yield. ¹H NMR (d6-DMSO): δ 9.89 (s,1H), 9.85 (m, 4H), 9.58 (s, 1H), 8.03 (t, J=1.2 Hz, 1H), 7.21 (d, J=2.0Hz, 1H), 7.18 (d, J=1.9 Hz), 7.15 (d, J=2.0 Hz, 1H), 7.01 (d, J=1.9 Hz,1H), 7.00 (d, J=1.9 Hz, 1H), 6.80 (d, J=1.5 Hz, 1H), 6.35 (d, J=1.4 Hz,1H), 6.24 (d, J=2.0 Hz, 1H), 3.82 (s, 6H), 3.77 (s, 3H), 3.71 (s, 3H),3.23 (q, J=6.8, 23.3 Hz, 2H), 2.21 (t, J=7.1 Hz, 2H), 2.11 (s, 6H), 1.58(m, 2H). LC/MS (ESI): m/z=597.67 (M+H).

EC2192. EC2169 (28.3 mg, 0.1 mmol) and EC2166 (56.1 mg, 0.1 mmol) weredissolved in DMF (1.2 mL). The solution was treated with PyBOP (104.1mg, 0.2 mmol) and DIPEA (69.7 μL, 0.4 mmol) at ambient temperature underAr. The reaction was stirred for 2 h and purified with CombiFlash in0-20% MeOH/DCM+0.1% TEA. 30.3 mg of EC2192 is obtained (35%). LCMS:[M+H]⁺ m/z=856.

EC2193. EC2192 (30.3 mg, 0.035 mmol) was converted to EC2194 inTHF/MeOH/H2O (0.9/0.3/0.3 mL) by LiOH (1M solution, 0.3 mL) at ambienttemperature. EC2194 was isolated under reduced pressure. LCMS: [M+H]⁺m/z=842. EC 2186 (0.044 mmol, 25.4 mg) and EC2194 (0.035 mmol) weremixed in THF/DMF (1 mL/0.5 mL) and treated with PyBOP (36.4 mg, 0.07mmol) and DIPEA (12.2 μL/0.07 mmol) at ambient temperature under Ar. Thereaction was stirred for 2-3 h then separated with CombiFlash in 0-20%MeOH/DCM+0.1% TEA to obtain EC2193 (14.7 mg, 35%). LCMS: [M+H]⁺m/z=1192.

A mixture of methyl vanillate (402.2 mg, 2.21 mmol), EC2153 (502.9 mg,2.43 mmol), and K₂CO₃ (0.6 g, 4.42 mmol) in anhydrous acetone (8.84 mL)was heated with stirring at 60° C. for 1.5 hr. The reaction was cooledto ambient temperature, the solid was filtered out, and concentratedunder reduced pressure to give a residue, which was purified byCombiFlash in 0-25% EtOAc/p-ether to give 678.8 mg of EC2314 (yield99%). LCMS: [M+H]⁺ m/z=309. ¹H NMR (500 MHz, CDCl₃) δ 7.64 (dd, J=8.80,1.96 Hz, 1H), 7.53 (d, J=1.96 Hz, 1H), 5.90 (m, 1H), 5.32 (dd, J=17.60,1.95 Hz, 1H), 5.23 (dd, J=10.27, 0.98 Hz, 1H), 4.59 (dd, J=5.87, 1.47Hz, 2H), 4.13 (t, J=6.35 Hz, 2H), 3.90 (s, 3H), 3.89 (s, 3H), 2.58 (t,J=7.09 Hz, 2H), 2.19 (m, 2H).

A mixture of EC2314 (598.9 mg, 1.94 mmol) in acetic anhydride (9.7 mL)was cooled to 0° C. and treated with Cu(NO₃)₂.3H₂O by slow addition. Thereaction was kept at 0° C. for 1 h. The reaction was stirred at rt for 2hrs. The reaction was poured into a stirred ice water and stirred for 1hr. The reaction mixture in water was extracted with EtOAc (3×). Thecombined organic phase was washed with water and dried over anhydrousNa₂SO₄ and concentrated under reduced pressure. The residue was loadedonto a CombiFlash system for purification (silica gel, gradient elution:0-25% EtOAc in p-ether) to produce 559.7 mg EC2315 in a yield of 82%.LCMS: [M+H]⁺ m/z=354. ¹H NMR (500 MHz, CDCl₃): 7.43 (s, 1H), 7.05 (s,1H), 5.89 (m, 1H), 5.30 (d, J=17.1 Hz, 1H, 5.22 (d, J=10.27 Hz, 1H),4.58 (d, J=6.84 Hz, 2H), 4.57 (t, J=6.36 Hz, 2H), 4.11 (s, 3H), 3.92 (s,3H), 2.57 (t, J=7.34 Hz, 2H), 2.19 (m, 2H). ¹³C NMR (500 MHz, CDCl₃):172.39, 166.27, 152.78, 149.64, 141.12, 132.04, 121.62, 118.42, 110.96,108.13, 68.41, 65.27, 56.52, 53.19, 30.38, 24.14.

The mixture of EC2315 (559.7 mg, 1.58 mmol) and Pd(PPh₃)₄ was dissolvedin pre-mixed piperidine (1.1 mL, 11.06 mmol) and formic acid (417.3 μL,11.06 mmol) in DCM (40 mL). To that solution was added water (1.0 mL)and the reaction was stirred at rt for 30 min. When the reaction wascompleted, the solvent was removed in vacuo, the residue was loaded toCombiFalsh in 0-20% MeOH/DCM to give the correspondent acid EC2316 as asolid (264.6 mg, yield 53%). LCMS: [M+H]⁺ m/z=314.52. ¹H NMR (500 MHz,MeOH-d4) δ: 7.55 (s, 1H), 7.23 (s, 1H), 4.15 (t, J=5.86 Hz, 2H), 3.95(s, 3H), 3.87 (s, 3H), 2.51 (t, J=7.34 Hz, 2H), 2.11 (m, 2H).

The solution of EC2166 (107.1 mg, 0.18 mmol) and EC2316 (56.8 mg, 0.18mmol) in anhydrous DMF (1 mL) was treated with PyBOP (187.3 mg, 0.36mmol) and DIPEA (125.4 μL, 0.72 mmol) at rt for 2 hr under Ar. Thereaction was purified with CombiFalsh (silica, 0-20% MeOH/DCM) to giveEC2365 (79.3 mg, yield 50%). LCMS: [M+H]⁺ m/z=886.97. ¹³C NMR (500 MHz,MeOH-d4) δ: 162.82, 152.88, 123.26, 121.89, 121.10, 119.40, 118.99,110.81, 107.97, 105.14, 104.51, 68.59, 56.91, 55.63, 52.12, 43.94,37.13, 35.36, 35.30, 32.21, 26.82, 24.87. ¹H NMR (500 MHz, MeOH-d4)δ:7.54 (s, 1H), 7.20 (s, 1H), 7.16 (m, 3H), 7.11 (d, J=1.95 Hz, 1H),6.92 (m, 2H), 6.82 (d, J=1.96 Hz, 1H), 6.78 (d, J=1.96 Hz, 1H), 4.17 (t,J=5.87 Hz, 2H), 3.88 (m, 12H), 3.86 (s, 6H), 3.33 (m, 2H), 2.53 (t,J=7.34 Hz, 2H), 2.43 (m, 2H), 2.28 (s, 6H), 2.21 (m, 2H), 1.78 (m, 2H).

EC2363 (68.9 mg, 0.078 mmol) was dissolved in THF/MeOH/water (3:1:1, 1.6mL) and treated with LiOH (0.33 mmol) at rt for 3 hrs. Then the reactionwas diluted with MeOH (2.0 mL) and treated with Pd/C (10% wt, 10 mg)under H2 balloon at rt for overnight. The reaction was filtered througha pad of celite and concentrated in vacuo. The obtained amino acid(EC2194) was used for the next step without further purification. LCMS:[M+H]⁺ m/z=842.85.

The solution of EC2194 (33.0 mg, 0.039 mmol) and EC2186 (17.3 mg, 0.047mmol) in DMF (0.5 mL) was treated with PyBOP (40.6 mg, 0.078 mmol) andDIPEA (27.2 μL, 0.156 mmol) at rt for overnight. The reaction waspurified with prep-HPLC (10 to 100% ACN in 50 mM NH₄HCO₃, pH 7.4) togive the product (8.4 mg, EC2193, low yield due to the instrument issueduring the purification). LCMS: [M+H]⁺ m/z=1192.

EC1579 (14.4 mg, 0.0086 mmol) was dissolved in DMSO (0.5 mL) at rt underAr, and to which was added the solution of EC2193 (8.4 mg, 0.0071 mmol)in DMSO (0.5 mL). The reaction mixture was treated with TEA (5.9 μL,0.043 mmoL) and stirred at rt for 30 min under Ar. The reaction waspurified with prep-HPLC (10 to 100% ACN in 50 mM NH₄HCO₃, pH 7.4) togive the conjugate EC2201 (8.0 mg, 41% yield). LCMS: [M+2H]²⁺m/z=1380.56; [M+3H]³⁺ m/z=921.89. ¹H NMR (500 MHz, DMSO-d₆, D₂O drops,selected data) δ: 8.57 (s, 1H), 7.54 (d, J=8.80 Hz, 2H), 7.20 (m, 4H),6.87 (m, 2H), 6.77 (m, 2H), 6.58 (d, J=8.80 Hz, 3H), 6.31 (d, J=13.69Hz, 1H), 4.95 (d, br, 2H).

Imidazole carboxylic acid (35.03 mg, 0.145 mmol) and EC2163 (56.7 mg,0.121 mmol) were dissolved in DMF (2 mL) and treated with PyBOP (126.0mg, 0.242 mmol) and DIPEA (84.3 μL, 0.484 mmol) at rt under Ar. Thereaction was stirred for 1 hr and then loaded to CombiFlash ((silicagel, gradient elution: 0-20% MeOH in DCM and 0.1% TEA) to give 90.1 mgof EC2313 in a yield of 93%. LCMS: [M+H]⁺ m/z=692.9. Prior to the nextstep, the Boc group in EC2313 was deprotected with 50% TFA in DCM at rtfor 0.5 hr to the amine TFA salt product which was used directly afterthe solvent and TFA were removed in vacuo.

EC2313 (90.1 mg, 0.13 mmol) was treated with 50% TFA/DCM at rt for 0.5hr. the solvent was then removed in vacuo and redissolved in DMF (0.5mL). To the solution was added EC2316 (40.8 mg, 0.13 mmol), PyBOP (134.3mg, 0.26 mmol) and DIPEA (90.6 μL, 0.52 mmol). The reaction was stirredovernight at rt. The reaction was purified with prep-HPLC (10 to 100%ACN in 50 mM NH₄HCO₃, pH 7.4). 78.1 mg of the desired product EC2364 wasobtained (68% yield). LCMS: [M+H]⁺ m/z=887.8. ¹H NMR (500 MHz, MeOH-d₄,selected data) δ: 7.56 (s, 1H), 7.38 (s, 1H), 7.26 (d, J=1.96 Hz, 1H)7.21 (s, 1H), 7.19 (d, J=1.46 Hz, 1H) 7.17 (d, J=1.95 Hz, 1H), 6.95 (m,2H), 6.85 (d, J=1.96 Hz, 1H) 4.20 (t, J=5.87 Hz, 2H), 4.03 (s, 3H), 3.93(s, 3H), 3.91 (s, 3H) 3.89 (s, 3H), 3.88 (s, 3H), 3.87 (s, 3H) 3.85 (s,3H).

EC2364 (78.1 mg, 0.088 mmol) was converted to an acid in THF/MeOH(0.9/0.3 mL) by LiOH (1M solution, 0.3 mL) at rt. LCMS: [M+H] m/z=873.8.To the reaction mixture was added Pd/C (10%, wet) after flushed with H₂.The reaction was stirred under hydrogen balloon overnight at rt. Themixture was filtered through a pad of celite and concentrated to givethe amino acid EC2367 which was used for the next step without furtherpurification. 59.7 mg (81% yield). LCMS: [M+H]⁺ m/z=843.8.

Amino acid EC2367 (59.7 mg, 0.071 mmol) in DMF (0.5 mL) was coupled withEC2186 (29.4 mg, 0.08 mmol) in the presence of PyBOP (73.9 mg, 0.142mmol) and DIPEA (49.5 μL, 0.284 mmol) overnight at rt. The product waspurified with prep-HPLC (10 to 100% ACN in 50 mM NH₄HCO₃, pH 7.4) toprovide EC2366 (8.1 mg, 10% for 3 steps). LCMS: [M+2H]²⁺ m/z=597.2.

EC2366 (8.1 mg, 0.0068 mmol) in MeOH (0.5 mL) was added to the solutionof EC1579 (15.0 mg, 0.0089 mmol) in DMSO (1 mL) at rt under Ar. Thereaction was stirred for 0.5-1 hr. The reaction was purified withprep-HPLC (10 to 100% ACN in 50 mM NH₄HCO₃, pH 7.4) to give 3.0 mg ofthe product EC2368 (16% yield). LCMS: [M+3H]³⁺ m/z=921, [M+2H]²⁺m/z=1382. ¹H NMR (500 MHz, DMSO-d₆, D₂O drops, selected data) δ: 8.57(s, br., 1H), 7.57 (s, br., 2H), 7.38 (s, 1H), 7.24 (s, 1H), 7.19 (s,1H), 7.14 (s, 1H), 7.05 (s, 1H), 6.98 (s, 1H), 6.77 (s, 1H), 6.61 (s,br, 3H), 6.33 (s, 1H).

EC2169. A mixture of EC2168 (982 mg, 3.04 mmol) and Pd(PPh₃)₄ (422 mg,0.365 mmol) was dissolved in a pre-mixed solution of piperidine (2.10mL)/formic acid (0.802 mL)/DCM (98.0 mL), followed by addition of water(2.0 mL). The reaction mixture was stirred at ambient temperature for 30min, the volume was reduced to about half of the original under reducedpressure, and loaded onto a CombiFlash system for purification (Column:silica gel. Gradient elution: 0-2% MeOH in DCM) to produce 725 mg EC2169as a light ivory solid. MS (ESI m/z) calculated for C₁₃H₁₈NO₆ (M+H)⁺:284.11; found 284.14.

EC2184. To a solution of EC2169 (20 mg, 0.070 mM) and EC2163 (34.4 mg,0.060 mM) in DMF (1 mL) was added PyBop (54.6 mg, 0.105 mM) and DIPEA(0.122 mL, 0.70 mM). The reaction was allowed to stir for 30 min. LCMSanalysis (20 mM NH₄HCO₃, pH 7.4) indicated that the reaction wascomplete. The reaction mixture was loaded onto a CombiFlash (SiO₂)column and eluted with 0-30% MeOH in CH₂Cl₂ to yield pure EC2184 (22 mg,50%). LCMS (ESI): (M+H)⁺=Calculated for C₃₆H₄₈N₉O₈, 734.35; found 734.39

EC2185. To a solution of EC2184 (19 mg, 0.026 mM) in THF/MeOH (1 mL/0.33mL) was added LiOH.H₂O (6.5 mg, 0.155 mM) in 0.33 mL of water. Thereaction was allowed to stir for 18 h. LCMS analysis (20 mM NH₄HCO₃, pH7.4) indicated that the reaction was complete. The reaction mixture wasconcentrated to remove organic solvents and acidified with 2M HCl to pH2 and freeze dried for 2 days. The isolated product was used withoutfurther purification. LCMS (ESI): (M+H)⁺=Calculated for C₃₅H₄₆N₉O₈,720.34; found 720.46

To a solution of EC2316 (33.4 mg, 0.107 mM) and EC2163 (50 mg, 0.107 mM)in DMF (1 ml) was added PyBop (83.5 mg, 0.161 mM) and DIPEA (0.075 ml,0.70 mM) respectively. The reaction was allowed to stir for 3 h. LCMSanalysis (20 mM NH₄HCO₃, pH 7.4) indicated that the reaction wascomplete. The reaction mixture was loaded onto a combiflash (SiO₂)column and eluted with 0-30% MeOH in CH₂Cl₂ (0.2% TEA) to yield pureEC2415 (30 mg, 37%). ¹H NMR (500 MHz, CD₃OD): δ 7.51 (s, 1H), 7.17 (s,1H), 7.14 (m, 2H), 7.10 (d, J=2 Hz, 1H), 6.89 (d, J=2 Hz, 1H), 6.80 (d,J=1.5 Hz, 1H), 6.76 (d, J=2 Hz, 1H), 4.14 (t, J₁=6.0 Hz, J₂=6.5 Hz, 2H),3.87 (s, 6H), 3.86 (s, 3H), 3.85 (s, 3H), 3.84 (s, 3H), 3.31 (t, J₁=7.0Hz, J₂=7.5 Hz, 2H), 2.52 (t, J₁=7.5 Hz, J₂=7.5 Hz, 2H), 2.39 (t, J₁=8.5Hz, J₂=7.0 Hz, 2H), 2.25 (s, 6H), 2.17 (m, 2H), 1.75 (m, 2H); LCMS(ESI): (M+H)⁺=Calculated for C₃₆H₄₅N₉O₁₀, 764.33; found 764.38

To a solution of EC2415 (30 mg, 0.039 mM) in THF/MeOH (0.6 mL/0.2 mL)was added LiOH.H₂O (4.9 mg, 0.118 mM) in 0.2 mL of water. The reactionwas allowed to stir for 24 h. LCMS analysis (20 mM NH₄HCO₃, pH 7.4)indicated that the reaction was complete. The reaction mixture wasdiluted with methanol (1.0 mL), 10% Pd/C (6 mg) was added. Reactionmixture was stirred under H₂ atmosphere (balloon) for 24 h. LCMSanalysis (20 mM NH₄HCO₃, pH 7.4) indicated that the reaction wascomplete (same retention time as starting material but mass isdifferent). Reaction mixture was filtered over celite pad andconcentrated. Crude product (EC2185) was dried and directly used fornext reaction. LCMS (ESI): (M+H)⁺=Calculated for C₃₅H₄₅N₉O₈, 720.34;found 720.40

EC1693 (21 mg, 0.045 mM) was treated with the mixture ofTFA/dichloromethane/TIPS (1 mL/1 mL/0.05 mL) and stirred for 30 min.LCMS analysis (20 mM NH₄HCO₃, pH 7.4) indicated that the reaction wascomplete. The reaction mixture was concentrated to dryness,co-evaporated with DCM (3 times) and dried under high vacuum for 1 h toyield EC2186. In another flask, EC2185 (28 mg, 0.039 mM, from previousreaction) was dissolved in dry DMF (1 mL). PyBop (40.6 mg, 0.078 mM) andDIPEA (0.136 mL, 0.78 mM) were added respectively. After the reactionmixture stirred for 5 min, EC2186 (prepared earlier) in DCM (1 mL) wasadded, and stirred for 1 h. LCMS analysis (20 mM NH₄HCO₃, pH 7.4)indicated that the reaction was complete. The reaction mixture waspurified with prep-HPLC (10 to 100% acetonitrile in 20 mM NH₄HCO₃, pH7.4) to yield pure EC2187 (22 mg, 53%, over 3 steps). ¹H NMR (500 MHz,CD₃OD): δ 8.40 (m*, 1H), 8.37 (m*, 1H), 8.16 (m*, 1H), 7.84-7.70 (m*,2H), 7.26-7.20 (m*, 1H), 7.17 (m*, 1H), 7.13 (d, J=1.5 Hz, 1H), 6.92 (d,J=1.5 Hz, 1H), 6.82 (dd, J₁=6 Hz, J₂=1.5 Hz, 2H), 6.42 (s, 1H), 5.14 (d,J=5 Hz, 1H) 5.10-4.94 (m*, 3H), 4.50-4.06 (m*, 5H), 4.04 (t, J₁=6 Hz,J₂=6.5 Hz, 2H), 3.90 (s, 3H), 3.88 (s, 3H), 3.87 (s, 3H), 3.85 (m*, 1H),3.73 (s, 3H), 3.36 (t, J 1=6 Hz, J₂=7 Hz, 2H), 3.33 (m*, 1H), 3.20-3.00(m*, 5H), 2.72 (m*, 2H), 2.55 (m*, 2H), 2.53 (s, 6H), 2.20-2.12 (m*,2H), 1.85 (m, 2H); LCMS (ESI): (M+H)⁺=Calculated for C₅₁H₆₅N₁₂O₁₀S₂,1069.43; found 1069.60 * Due to diasteromeric and/or rotameric nature ofthe compound

EC1579 (13.3 mg, 0.0079 mmol) in DMSO (0.5 mL) under Argon was stirredto a clear solution and to which was added the solution of EC2187 (7 mg,0.0066 mmol) in DMSO (0.5 mL) followed by addition of DIPEA (0.023 mL,0.131 mmol). The reaction was stirred for 1 hr at r.t. under Argon. Theproduct was isolated with prep-HPLC in 10-100% MeCN/pH 7 buffer to giveEC2188, 10.4 mg (60% in yield) as a solid after lyophilized. ¹H NMR (500MHz, DMSO-D₆+D₂O) (selected data): δ 8.59 (s, 1H), 7.57 (d, J=8.5 Hz,2H), 7.20 (d, J=2 Hz, 1H), 7.16 (d, J=2 Hz, 1H), 7.13 (d, J=1.5 Hz, 1H),6.94 (d, J=2 Hz, 1H), 6.82 (d, J=1.5 Hz, 1H), 6.77 (d, J=2 Hz, 1H), 6.60(d, J=9 Hz, 2H), 6.58 (m, 1H), 6.33 (s, 1H), 4.97 (s, 2H), 4.93 (s, 1H),4.45 (s, 2H); LCMS: [M+2H]²⁺ m/z=Calculated for C₁₁₁H₁₅₇N₂₇O₄₄S₂,1319.02; found 1319.51

A solution of EC1770 (111 mg) and diethylamine (2.0 mL) in anhydrous DCM(5.0 mL) was stirred at ambient temperature under argon for 90 min,concentrated, co-evaporated with DCM (3 mL×3), dried under vacuum for 60min, re-dissolved in DCM (20 mL), and mixed with a solution of NaHSO₃(14.6 mg) in water (20 mL). The reaction mixture was stirred at ambienttemperature for 60 min and separated. The organic layer was extractedwith water (15 mL) and the combined aqueous layers were freeze-dried toyield 86.5 mg (101%) EC2322 as a beige solid. ¹H NMR (500 MHz, 298 K,DMSO-d6) δ 7.301 (s, 1H), 6.968 (s, 1H), 6.478 (s, 1H), 6.220 (s, 1H),5.078 (s, 1H), 5.026 (s, 1H), 4.215 (d, J=17.0 Hz, 1H), 3.953 (m, 4H),3.884 (m, 2H), 3.714 (d, J=22.5 Hz, 1H), 3.669 (s, 3H), 3.596 (s, 3H),3.151 (d, J=14.0 Hz, 1H), 2.830 (m, 1H), 1.757 (m, 4H), 1.525 (m, 2H).MS− (ESI m/z) calculated for C₂₇H₃₂N₃O₁₀S: 590.18; found 590.27.

EC1693 (19.8 mg) was dissolved in a solution of TFA (0.15 mL) and DCM(0.85 mL), stirred at ambient temperature for 30 min, concentrated,co-evaporated with DCM (1 mL×3), and dried under vacuum for 60 min. Theresidue was dissolved in anhydrous DMF (2.5 mL) and transferred into asmall vial containing EC2322 (18.3 mg) and PyBOP (19.4 mg). To theresulting solution was added TEA (32.0 μL). The reaction mixture wasstirred at ambient temperature under argon for 15 min and a solution ofEC1579 (76.1 mg) in buffer (50 mM NH₄HCO₃, pH 7.0, 7.0 mL) was added.The resulting homogeneous solution was stirred at ambient temperatureunder argon for 15 min and loaded directly onto a preparative HPLC(Mobile phase A: 50 mM NH₄HCO₃ buffer, pH 7.0; B=ACN. Method: 10-80 B %in 20 min.) for purification to produce 7.9 mg (10.6%) EC2323 as a paleyellow solid. Selective ¹H NMR (500 MHz, 298 K, D₂O) δ 8.671 (s, 1H),7.711 (b, 2H), 7.146 (s, 1H), 6.824 (b, 3H), 6.728 (s, 1H), 6.419 (b,2H). MS− (ESI m/2z) calculated for C₁₀₃H₁₄₄N₂₁O₄₆S₃: 1253.44; found1253.89.

TEA (80.0 μL) was added to a solution of EC2351 (25.3 mg), EC2160 (57.1mg), and PyBOP (42.9 mg) in anhydrous DMF (3.5 mL). The reaction mixturewas stirred at ambient temperature under argon for 15 min and passedthrough a flash column eluting with 0-10% MeOH in DCM) to yield 62.4 mg(99.1%) crude EC2361 as a beige solid, which was used in the next stepwithout further purification. MS⁺ (ESI m/z) calculated for C₄₂H₅₀N₉O₁₀:840.37; found 840.47.

A mixture of EC2361 (62.4 mg), Pd(PPh₃)₄ (14.7 mg), piperidine (51.4μL), formic acid (19.6 μL), and water (30.0 μL) in DCM (3.0 mL) wasstirred at ambient temperature for 25 min, then loaded directly onto aCombiFlash system (silica gel column. Gradient: 0-10% MeOH in DCM) forpurification to yield 20.7 mg (34.8%) EC2362 as a beige solid. ¹H NMR(500 MHz, 298 K, CD₃OD) 7.360 (s, 1H), 7.319 (s, 1H), 7.217 (s, 1H),7.189 (s, 1H), 7.135 (s, 1H), 6.937 (s, 1H), 6.931 (s, 2H), 6.833 (s,1H), 6.334 (s, 1H), 4.013 (t, J=6.5 Hz, 2H), 3.919 (s, 6H), 3.908 (s,3H), 3.895 (s, 3H), 3.803 (s, 3H), 3.723 (s, 3H), 2.368 (t, J=7.0 Hz,2H), 1.872 (m, 2H), 1.793 (m, 2H), 1.585 (m, 2H). MS⁺ (ESI m/z)calculated for C₃₉H₄₆N₉O₁₀: 800.34; found 840.63.

EC1693 (15.1 mg) was dissolved in a solution of TFA (0.20 mL) and DCM(1.5 mL), stirred at ambient temperature for 15 min, concentrated,co-evaporated with DCM (1.5 mL×3), and dried under vacuum for 60 min.The residue was dissolved in anhydrous DMF (1.5 mL) and transferred intoa small vial containing EC2362 (20.7 mg) and PyBOP (14.8 mg). To theresulting solution was added TEA (30.0 μL). The reaction mixture wasstirred at ambient temperature under argon for 10 min, diluted with DMSO(3.0 mL), and a solution of EC1579 (56.6 mg) in buffer (50 mM NH₄HCO₃,pH 7.0, 5.0 mL) was added. The reaction mixture was stirred at ambienttemperature under argon for 10 min, at 40° C. for an additional 10 min,and loaded directly onto a preparative HPLC (Mobile phase A: 50 mMNH₄HCO₃ buffer, pH 7.0; B=ACN. Method: 10-80 B % in 20 min.) forpurification to give 35.6 mg (50.6%) EC2363 as a pale yellow solid.Selective ¹H NMR (500 MHz, 298 K, D₂O) δ 8.438 (s, 1H), 7.476 (d, J=8.0Hz, 2H), 7.113 (s, 1H), 7.031 (s, 2H), 6.984 (s, 1H), 6.734 (s, 1H),6.686 (s, 2H), 6.643 (s, 1H), 6.531 (d, J=9.0 Hz, 2H), 6.262 (b, 1H).MS− (ESI m/2z) calculated for C₁₁₅H₁₅₆N₂₇O₄₆S₂: 1357.51; found 1357.89.

DIPEA (0.20 mL) was added dropwise to a solution of EC2160 (115.0 mg)and 6-bromohexanoyl chloride (55.0 μL) in anhydrous DMF (3.2 mL). Thereaction mixture was stirred at ambient temperature under argon for 5min, diluted with DMSO (10 mL), and loaded onto a preparative HPLC(Mobile phase A: 50 mM NH₄HCO₃ buffer, pH 7.0; B=ACN. Method: 10-100 B %in 20 min) for purification to give 66.5 mg EC2270 as a white solid. MS(ESI m/z) calculated for C₃₁H₃₈BrN₈O₆ (M+H)⁺: 697.21; found 697.53.

A mixture of EC2267 (15.0 mg), EC2270 (18.7 mg), and K₂CO₃ (26.1 mg) inanhydrous DMF (2.0 mL) was heated with stirring at 80° C. in a sealedvessel for 8 min, cooled in an ice-bath, diluted with DMSO (7.5 mL),filtered, and the filtrate was loaded onto a preparative HPLC (Mobilephase A: 50 mM NH₄HCO₃ buffer, pH 7.0; B=ACN. Method: 10-100 B % in 20min) for purification to produce 11.5 mg EC2292 as a white solid. MS(ESI m/z) calculated for C₄₂H₅₀N₉O₁₀ (M+H)⁺: 840.37; found 840.81.

A pre-mixed solution of piperidine (2.60 μL) and formic acid (0.994 μL)in DCM (980 μL) and water (20 μL) was added to a mixture of EC2292 (3.2mg) and Pd(PPh₃)₄ (0.70 mg) in tandem. The reaction mixture was stirredat ambient temperature under argon for 1 h and loaded directly onto aCombiFlash system (Column: silica gel. Mobile phase A: DCM; B: MeOH.Gradient: 0-10% B) for purification to give 1.2 mg EC2299 as a whitesolid. MS (ESI m/z) calculated for C₃₉H₄₆N₉O₁₀ (M+H)⁺: 800.34; found800.59.

EC1963 (1.4 mg) was dissolved in a solution of TFA (50 μL) and DCM (150μL), stirred at ambient temperature for 10 min, concentrated,co-evaporated with DCM (0.5 mL×3), and dried under vacuum for 1 h. Theresidue was dissolved in anhydrous DMF (350 μL) and transferred into asmall vial containing EC2299 (0.50 mg) and PyBOP (1.2 mg). To theresulting solution was added TEA (1.8 μL). The reaction mixture wasstirred at ambient temperature under argon for 15 min, diluted with DMSO(500 μL), and a solution of EC1579 (3.2 mg) in buffer (50 mM NH₄HCO₃, pH7.0, 1.3 mL) was added. The resulting homogeneous solution was stirredat ambient temperature under argon for 20 min and loaded directly onto apreparative HPLC (Mobile phase A: 50 mM NH₄HCO₃ buffer, pH 7.0; B=ACN.Method: 10-100 B % in 20 min) for purification to produce 0.35 mg EC2299as a white solid. MS (ESI m/2z) calculated for C₁₁₅H₁₅₉N₂₇O₄₆S₂[(M+2H)/2]⁺: 1359.02; found 1360.15.

A suspension of I (376 mg), 2-ethanolamine (80.6 μL), and MgSO₄ (960 mg)in DCM (20 mL) was stirred at ambient temperature under argon for 2 hr.The solid was filtered off and the filtrate was transferred into asolution of Fmoc-Glu-Oall (656 mg) and HATU (609 mg) in anhydrous DMF(6.0 mL), followed by addition of DIPEA (0.62 mL). After stirring atambient temperature under argon for 1 hr, the reaction mixture wasloaded directly onto a CombiFlash system (silica gel column. Gradient:0-50% EtOAc in petroleum ether) for purification to produce 365 mg(42.5%) EC2407 as a white solid. ¹H NMR (500 MHz, 298 K, CDCl₃) δ 7.764(b, 2H), 7.605 (b, 2H), 7.392 (b, 2H), 7.312 (b, 2H), 5.905 (m, 1H),5.495-4.979 (m, 3H), 5.004-4.928 (m, 2H), 4.655-3.409 (m, 13H),2.730-2.172 (m, 6H), 1.433 (m, 9H). MS⁺ (ESI m/z) calculated forC₃₉H₄₆N₉O₁₀: 800.34; found 840.63. MS⁺ (ESI m/z) calculated forC₃₆H₄₄N₃O₈: 646.31; found 646.50.

A solution of EC2407 (365 mg) and diethylamine (4.0 mL) in anhydrous DCM(4.0 mL) was stirred at ambient temperature under argon for 3.5 hr,concentrated, co-evaporated with DCM (5 mL×3), dried under vacuum for 60min, re-dissolved in DCM (45 mL) and DMF (1.0 mL), and added to amixture of Fmoc-Glu-O^(t)Bu (229 mg) and HATU (204 mg). The reactionmixture was stirred at ambient temperature under argon for 35 min,concentrated to a small volume, and loaded directly onto a CombiFlashsystem (silica gel column. Gradient: 0-70% EtOAc in petroleum ether) forpurification to yield 300 mg (67.2%) EC2438 as a white solid. ¹H NMR(500 MHz, 298 K, CDCl₃) δ 7.768 (d, J=7.5 Hz, 2H), 7.620 (d, J=7.5 Hz,2H), 7.398 (t, J=7.5 Hz, 2H), 7.317 (t, J=7.5 Hz, 2H), 5.901 (m, 1H),5.338 (d, J=19.5 Hz, 2H), 5.244 (m, 1H), 4.959 (m, 2H), 4.617 (m, 3H),4.375 (m, 2H), 4.220 (m, 2H), 4.116-3.813 (m, 4H), 3.611 (b, 1H), 3.388(m, 1H), 2.755-1.913 (m, 10H), 1.430 (m, 18H). MS⁺ (ESI m/z) calculatedfor C₄₅H₅₉N₄O₁₁: 831.42; found 831.65.

A solution of EC2408 (300 mg) and diethylamine (10.0 mL) in anhydrousDCM (5.0 mL) was stirred at ambient temperature under argon for 1.5 hr,concentrated, co-evaporated with DCM (10 mL×3), dried under vacuum for 1hr, and re-dissolved in DCM (10 mL). To this solution were added3-(Maleimido)propionic acid N-succinimidyl ester (115 mg) and DIPEA(0.15 mL) in tandem. The reaction mixture was stirred at ambienttemperature under argon for 50 min, concentrated to about half of theoriginal volume, and passed through a flash column eluting with 0-100%EtOAc in petroleum ether to give 138 mg (50.3%) crude EC2439 as a whitesolid, which was used in the next step without further purification. MS⁺(ESI m/z) calculated for C₃₇H₅₄N₅O₁₂: 760.38; found 760.56.

A mixture of EC2439 (192 mg), Pd(PPh₃)₄ (76.1 mg), piperidine (25.0 μL),and formic acid (9.53 μL) in DCM (5.0 mL) was stirred at ambienttemperature under argon for 1 hr. To the mixture was added TFA (2.5 mL).The reaction mixture was stirred at ambient temperature under argon for1.5 hr, concentrated, re-dissolved in DMSO (9.5 mL) and loaded directlyonto a preparative HPLC (Mobile phase A: 0.1% TFA buffer; B=ACN. Method:0-30 B % in 20 min.) for purification to afford 65.0 mg (45.6%) EC2446as a white solid. ¹H NMR (500 MHz, 298 K, DMSO-d6) δ 12.605 (b, 2H),8.270 (d, J=8.0 Hz, 1H), 8.111 (d, J=8.5 Hz, 1H), 7.002 (s, 2H), 5.415(s, 1H), 5.104 (s, 2H), 4.284 (m, 1H), 4.151 (m, 2H), 4.003 (m, 2H),3.867 (d, J=15.0 Hz, 1H), 3.789 (m, 2H), 3.600 (m, 2H), 3.546 (m, 1H),2.607 (m, 1H), 2.522 (m, 1H), 2.448 (m, 1H), 2.428 (m, 2H), 2.339 (m,1H), 2.195 (m, 2H), 2.047 (m, 2H), 1.741 (m, 2H). MS− (ESI m/z)calculated for C₂₅H₃₂N₅O₁₀: 562.22; found 562.53.

TEA (19.0 μL) was added to a solution of EC2322 (8.4 mg), EC2446 (8.4mg), and PyBOP (7.5 mg) in anhydrous DMF (3.0 mL) and the solution wasstirred at ambient temperature under argon for 60 min. To the solutionwas added a solution of EC1579 (25.3 mg) in buffer (50 mM NH₄HCO₃, pH7.0, 6.0 mL) and the reaction mixture was stirred at ambient temperatureunder argon for 20 min, then loaded directly onto a preparative HPLC(Mobile phase A: 50 mM NH₄HCO₃ buffer, pH 7.0; B=ACN. Method: 10-80 B %in 20 min.) for purification to produce 2.3 mg (5.8%) EC2451 as a paleyellow solid. Selective ¹H NMR (500 MHz, 298 K, D₂O) δ 8.688 (s, 1H),7.699 (d, J=8.0 Hz, 2H), 7.144 (s, 1H), 6.841 (b, 3H), 6.746 (s, 1H),6.497 (s, 1H). MS⁻ (ESI m/2z) calculated for C₁₁₇F₁₆₁N₂₄O₅₃S₂: 1407.01;found 1407.69.

EC2461 (10.4 mg) was dissolved in a solution of TFA (0.30 mL) and DCM(1.1 mL), stirred at ambient temperature for 30 min, concentrated,co-evaporated with DCM (2 mL×3), and dried under vacuum for 60 min. Theresidue was dissolved in anhydrous DMF (3.0 mL) and to which are addedEC2322 (9.3 mg) and PyBOP (8.1 mg), followed by TEA (21.0 μL). Thereaction mixture was stirred at ambient temperature under argon for 25min, diluted with DMF (1.5 mL), and a solution of EC1579 (32.1 mg) inbuffer (50 mM NH₄HCO₃, pH 7.0, 5.0 mL) was added. The resultinghomogeneous solution was stirred at ambient temperature under argon for10 min and loaded directly onto a preparative HPLC (Mobile phase A: 50mM NH₄HCO₃ buffer, pH 7.0; B=ACN. Method: 5-50 B % in 20 min.) forpurification to yield 7.3 mg (18%) EC2464 as a pale yellow solid.Selective ¹H NMR (500 MHz, 298 K, D₂O) δ 8.623 (s, 1H), 7.666 (b, 2H),7.089 (s, 1H), 6.780 (b, 3H), 6.687 (s, 1H), 6.492 (b, 2H). MS⁻ (ESIm/2z) calculated for C₁₁₅H₁₆₁N₂₄O₄₉S₂: 1363.02; found 1363.79.

To a solution of maleimidoethanol (0.655 mg, 4.64 mM) in dry DCM (5 ml)under Argon was added p-nitrophenylchloroformate (1.12 g, 5.56 mM) andDIPEA (1.13 ml, 6.50 mM) respectively. The reaction was allowed to stirat RT for 18 h. TLC analysis (5% methanol in methylene chloride)indicated that the reaction was complete. The reaction mixture wasconcentrated and purified using combiflash (SiO₂) column and eluted with0-100% EtOAc in petroleum ether to yield pure EC2474 (0.78 g, 55%). ¹HNMR (500 MHz, CDCl₃): δ 8.28 (d, J₁=9.0 Hz, 2H), 7.41 ((d, J₁=9.0 Hz,2H)), 6.77 (s, 2H), 4.41 (t, J₁=4.5 Hz, J₂=5.5 Hz, 2H), 3.95 (t, J₁=4.5Hz, J₂=5.5 Hz, 2H); ¹³C NMR (500 MHz, CDCl₃): δ 170.37, 155.40, 152.40,145.59, 134.36, 125.32, 121.99, 66.15, 36.35

To a solution of aldehyde (158 mg, 0.75 mM) in dry DCM (2 mL) was addedMgSO₄ (79 mg) and ethanolamine (67.83 μL, 1.13 mM) respectively. Thereaction was allowed to stir for 1 h. In another flask, EC2474 (459 mg,1.5 mM) was dissolved in dry DCM (2 mL) and triethyl amine (0.314 mL,2.25 mM) was added. Above reaction mixture (step 1) was slowly added tothis solution and stirred for 20 h. LCMS analysis (20 mM NH₄HCO₃, pH7.4) indicated that the reaction was complete (only mass no UV). TLCanalysis (50% EtOAc in petroleum ether) indicated that the reaction wascomplete. The reaction mixture was concentrated and purified usingcombiflash (SiO₂) column eluting with 0-50% EtOAc in petroleum ether toyield pure EC2475 (158 mg, 50%). ¹H NMR (500 MHz, CDCl₃): δ 6.72 (s,2H), 4.85-5.30 (m, 3H), 3.95-4.25 (m, 5H), 3.70-3.95 (m, 5H), 3.25 (brs, 1H), 2.40-2.85 (m, 2H), 1.41 (s, 9H); LCMS (ESI): (M+H)⁺=Calculatedfor C₂₀H₂₇N₃O₇, 422.18; found 422.39

EC2475 (10.0 mg, 0.025 mM) was treated with the mixture ofTFA/dichloromethane/TIPS (1.0 mL/1.0 mL/0.06 mL) and stirred for 30 min.LCMS analysis (20 mM NH₄HCO₃, pH 7.4) indicated that the reaction wascomplete. The reaction mixture was concentrated to dryness,co-evaporated with DCM (3 times) and dried under high vacuum for 1 h toyield EC2476. In another flask, EC2322 (13 mg, 0.02 mM) was dissolved indry DMF (1 mL). PyBop (11 mg, 0.02 mM) and TEA (29.5 μL, 0.21 mM) wereadded respectively. Stirred for 5 min, EC2476 (prepared earlier) in DMF(1 mL) was added, and stirred for 1 h. LCMS analysis (20 mM NH₄HCO₃, pH7.4) indicated that the product EC2477 was formed. EC1579 (50 mg, 0.03mM) in phosphate buffer (2 mL) was added and stirred for 1 h. LCMSanalysis (20 mM NH₄HCO₃, pH 7.4) indicated the product formation. Thereaction mixture was purified with prep-HPLC (5 to 80% acetonitrile in20 mM NH₄HCO₃, pH 7.4) to yield pure EC2478 (7.5 mg, 12%). ¹H NMR (500MHz, DMSO-D₆+D₂O) (selected data): δ 8.60 (s, 1H), 7.56 (d, J=8.0 Hz,2H), 6.94 (s, 1H), 6.60 (d, J=8.5 Hz, 2H), 6.60 (s, 1H), 6.49 (s, 1H),6.28 (br s, 1H), 5.06 (s, 1H), 5.01 (s, 1H), 4.90 (m, 2H), 4.45 (s, 4H);LCMS (ESI): [M−2H]²⁻=Calculated for C₁₀₇H₁₄₈N₂₂O₄₈S₂, 1286.28; found1286.31

The following examples are also described herein. It is to be understoodthat radicals of these examples are included in the PBD prodrugs,poly-PBD prodrugs, mixed PBDs, conjugates, and conjugates describedherein.

The following conjugates of PBD prodrugs, poly-PBD prodrugs, or mixedPBDs are described herein. The conjugates are prepared according to theprocesses described herein and conventional processes.

Method Examples

General. The following abbreviations are used herein: partial response(PR); complete response (CR), biweekly (M/F) (BIW), three times per week(M/W/F) (TIW). A PR is observed where tumor volume, as defined herein,decreases from a previous high during the observation period, thoughregrowth may occur. A CR is observed where tumor volume, as definedherein, decreases to zero during the observation period, though regrowthmay occur. A cure is observed where tumor volume, as defined herein,decreases to zero, and does not regrow during the observation period.

METHOD. Relative Affinity Assay. The affinity for folate receptors (FRs)relative to folate was determined according to a previously describedmethod (Westerhof, G. R., J. H. Schomagel, et al. (1995) Mol. Pharm. 48:459-471) with slight modification. FR-positive KB cells were heavilyseeded into 24-well cell culture plates and allowed to adhere to theplastic for 18 h. Spent incubation media was replaced in designatedwells with folate-free RPMI (FFRPMI) supplemented with 100 nM ³H-folicacid in the absence and presence of increasing concentrations of testarticle or folic acid. Cells were incubated for 60 min at 37° C. andthen rinsed 3 times with PBS, pH 7.4. Five hundred microliters of 1% SDSin PBS, pH 7.4, was added per well. Cell lysates were then collected andadded to individual vials containing 5 mL of scintillation cocktail, andthen counted for radioactivity. Negative control tubes contain only the³H-folic acid in FFRPMI (no competitor). Positive control tubes containa final concentration of 1 mM folic acid, and CPMs measured in thesesamples (representing non-specific binding of label) were subtractedfrom all samples. Relative affinities were defined as the inverse molarratio of compound required to displace 50% of ³H-folic acid bound to theFR on KB cells, where the relative affinity of folic acid for the FR wasset to 1.

EXAMPLE. The conjugates described herein show high binding affinitiestowards folate receptors as determined by an in vitro competitivebinding assay that measures the ability of the ligand to compete against³H-folic acid for binding to cell surface folate receptors (FR). Withoutbeing bound by theory, it is believed herein that the high bindingaffinity of the conjugates described herein allows for efficientcellular uptake via FR-mediated endocytosis.

METHOD. Inhibition of Cellular DNA Synthesis. The conjugates describedherein were evaluated using an in vitro cytotoxicity assay thatpredicted the ability of the drug to inhibit the growth of thecorresponding targeted cells, such as, but not limited to the following

Cell Line KB Human cervical carcinoma NCl/ADR-RES-Cl₂ Human ovariancarcinoma IGROV1 Human ovarian adenocarcinoma MDA-MB-231 Human breastadenocarcinoma (triple negative) A549 Human lung carcinoma H23 Humanlung adenocarcinoma HepG2 Human hepatocellular carcinoma AN3CA Humanendometrial adenocarcinomaIt is to be understood that the choice of cell type can be made on thebasis of the susceptibility of those selected cells to the drug thatforms the conjugate, and the relative expression of the cell surfacereceptor or target antigen. The test conjugates were conjugates of acell surface receptor or target antigen binding compound and PBDprodrugs, poly-PBD prodrugs, and mixed PBDs, as described herein. Thetest cells were exposed to varying concentrations of the conjugates, andoptionally also in the absence or presence of at least a 100-fold excessof the unconjugated cell surface receptor or target antigen bindingcompound for competition studies to assess activity as being specific tothe cell surface receptor or target antigen.

EXAMPLE. Conjugates of PBD prodrugs, poly-PBD prodrugs, and mixed PBDsdescribed herein were active against KB cells. The activity was mediatedby the folate receptor as indicated by competition experiments usingco-administered folic acid. KB cells were exposed for up to 7 h at 37°C. to the indicated concentrations of folate-drug conjugate in theabsence or presence of at least a 100-fold excess of folic acid. Thecells were then rinsed once with fresh culture medium and incubated infresh culture medium for 72 hours at 37° C. Cell viability was assessedusing a ³H-thymidine incorporation assay. For conjugates describedherein, dose-dependent cytotoxicity was generally measurable, and inmost cases, the IC₅₀ values (concentration of drug conjugate required toreduce ³H-thymidine incorporation into newly synthesized DNA by 50%)were in the low nanomolar range. Though without being bound by theory,when the cytotoxicities of the conjugates were reduced in the presenceof excess free folic acid, it is believed herein that such resultsindicate that the observed cell death was mediated by binding to thefolate receptor.

IC₅₀ KB Cells Example (nM) EC1628 383 EC1628 + DTT^((a)) 11 EC1629 +DTT^((a)) ≥10 EC1630 2.7 EC1673 ≥1 μM EC1695 ≥100 EC1695 + DTT^((a)) 1EC1704 0.46 EC1744 1.2 EC1772 0.33 EC1788 0.18 EC1879 0.56 EC1884 0.36EC1904 ≥50 EC1911 0.7 EC1949 1.49 EC2074 3.6 EC2080 0.2 EC2103 3.5EC2127 1.34 ^((a))Co-administered with dithiothreitol (DTT).

METHOD. In vitro activity against various cancer cell lines. IC₅₀ valueswere generated for various cell lines. Cells were heavily seeded in24-well Falcon plates and allowed to form nearly confluent monolayersovernight. Thirty minutes prior to the addition of the test compound,spent medium was aspirated from all wells and replaced with freshfolate-deficient RPMI medium (FFRPMI). A subset of wells were designatedto receive media containing 100 μM folic acid. The cells in thedesignated wells were used to determine the targeting specificity.Without being bound by theory it is believed herein that the cytotoxicactivity produced by test compounds in the presence of excess folicacid, i.e. where there is competition for FR binding, corresponded tothe portion of the total activity that was unrelated to FR-specificdelivery. Following one rinse with 1 mL of fresh FFRPMI containing 10%heat-inactivated fetal calf serum, each well received 1 mL of mediumcontaining increasing concentrations of test compound (4 wells persample) in the presence or absence of 100 μM free folic acid asindicated. Treated cells were pulsed for 2 h at 37° C., rinsed 4 timeswith 0.5 mL of media, and then chased in 1 mL of fresh medium up to 70h. Spent medium was aspirated from all wells and replaced with freshmedium containing 5 μCi/mL ³H-thymidine. Following a further 2 h 37° C.incubation, cells were washed 3 times with 0.5 mL of PBS and thentreated with 0.5 mL of ice-cold 5% trichloroacetic acid per well. After15 min, the trichloroacetic acid was aspirated and the cell materialsolubilized by the addition of 0.5 mL of 0.25 N sodium hydroxide for 15min. A 450 μL aliquot of each solubilized sample was transferred to ascintillation vial containing 3 mL of Ecolume scintillation cocktail andthen counted in a liquid scintillation counter. Final results wereexpressed as the percentage of ³H-thymidine incorporation relative tountreated controls.

METHOD. Inhibition of Tumor Growth in Mice. Four to seven week-old mice(Balb/c or nu/nu strains) were purchased from Harlan Sprague Dawley,Inc. (Indianapolis, Ind.). Normal rodent chow contains a highconcentration of folic acid (6 mg/kg chow); accordingly, test animalswere maintained on a folate-free diet (Harlan diet # TD00434) for about1 week before tumor implantation to achieve serum folate concentrationsclose to the range of normal human serum, and during the Method. Fortumor cell inoculation, 1×10⁶ M109 cells (a syngeneic lung carcinoma) inBalb/c strain, or 1×10⁶ KB cells in nu/nu strain, in 100 μL wereinjected in the subcutis of the dorsal medial area (right axilla).Tumors were measured in two perpendicular directions every 2-3 daysusing a caliper, and their volumes were calculated as 0.5×L×W², whereL=measurement of longest axis in mm and W=measurement of axisperpendicular to L in mm. Log cell kill (LCK) and treated over control(T/C) values were then calculated according to published procedures(see, e.g., Lee et al., “BMS-247550: a novel epothilone analog with amode of action similar to paclitaxel but possessing superior antitumorefficacy” Clin Cancer Res 7:1429-1437 (2001); Rose, “Taxol-basedcombination chemotherapy and other in vivo preclinical antitumorstudies” J Natl Cancer Inst Monogr 47-53 (1993)).

Dosing was initiated when the s.c. tumors had an average volume between50-100 mm³ (to), typically 8 days post tumor inoculation (PTI) for KBtumors, and 11 days PTI for M109 tumors. Test animals (5/group) wereinjected intravenously, generally three times a week (TIW), for 3 weekswith varying doses, such as with 1 μmol/kg to 5 μmol/kg, of the drugdelivery conjugate or with an equivalent dose volume of PBS (control),unless otherwise indicated. Dosing solutions were prepared fresh eachday in PBS and administered through the lateral tail vein of the mice.

METHOD. General 4T-1 Tumor Assay. Six to seven week-old mice (femaleBalb/c strain) were obtained from Harlan, Inc. (Indianapolis, Ind.). Themice were maintained on Harlan's folate-free chow for a total of threeweeks prior to the onset of and during the method. Folatereceptor-negative 4T-1 tumor cells (1×10⁶ cells per animal) wereinoculated in the subcutis of the right axilla. Approximately 5 dayspost tumor inoculation when the 4T-1 tumor average volume was −100 mm³(to), mice (5/group) were injected i.v. three times a week (TIW), for 3weeks with varying doses, such as 3 μmol/kg, of drug delivery conjugateor with an equivalent dose volume of PBS (control), unless otherwiseindicated herein. Tumor growth was measured using calipers at 2-day or3-day intervals in each treatment group. Tumor volumes were calculatedusing the equation V=a×b²/2, where “a” was the length of the tumor and“b” was the width expressed in millimeters.

METHOD. Drug Toxicity. Persistent drug toxicity was assessed bycollecting blood via cardiac puncture and submitting the serum forindependent analysis of blood urea nitrogen (BUN), creatinine, totalprotein, AST-SGOT, ALT-SGPT plus a standard hematological cell panel atAni-Lytics, Inc. (Gaithersburg, Md.). In addition, histopathologicevaluation of formalin-fixed heart, lungs, liver, spleen, kidney,intestine, skeletal muscle and bone (tibia/fibula) was conducted byboard-certified pathologists at Animal Reference Pathology Laboratories(ARUP; Salt Lake City, Utah).

METHOD. Toxicity as Measured by Weight Loss. The percentage weightchange of the test animals was determined on selected days post-tumorinoculation (PTI), and during dosing. The results were graphed.

EXAMPLE. In vivo activity against tumors. Conjugates described hereinshowed high potency and efficacy against KB tumors in nu/nu mice.Conjugates described herein showed specific activity against folatereceptor expressing tumors, with low host animal toxicity.

EXAMPLE. EC1629 in vivo activity against tumors. As shown in FIG. 1,EC1629 (♦) dosed at 2 μmol/kg TIW for two weeks decreased KB tumors intest animals compared to untreated control (●). Toxicity was notobserved, as evidenced by test animal total body weight.

EXAMPLE. EC1744 and EC1788 in vivo activity against tumors. As shown inFIG. 2 EC1744 (▪) dosed at 2 μmol/kg TIW for two weeks and EC1788 (▴)dosed at 0.2 μmol/kg TIW for two weeks decreases KB tumors in testanimals compared to untreated control (●). Moreover, EC1788 gave acomplete response. Toxicity was not observed for EC1744, as evidenced bytest animal total body weight. Minor toxicity was observed for EC1788,as evidenced by test animal total body weight; however, test animaltotal body weight steadily increased after the last dosing day.

EXAMPLE. EC1884, EC1879, and EC1788 in vivo activity against tumors. Asshown in FIG. 3, EC1884 (d) dosed at 2 μmol/kg TIW for two weeksdecreases KB tumors in test animals compared to untreated control (a).Toxicity was not observed for EC1884, as evidenced by test animal totalbody weight. FIG. 3 also shows and that EC1879 (c) dosed at 2 μmol/kgTIW for 1 week decreased KB tumors in test animals compared to untreatedcontrol (a). Moreover, EC1879 gave a partial response. Minor toxicitywas observed for EC1879, as evidenced by test animal total body weight.FIG. 3 also shows and that EC1788 (b) dosed at 0.4 μmol/kg BIW for 2weeks decreases KB tumors in test animals compared to untreated control(a). Moreover, EC1788 gave a complete response, and cure. Minor toxicitywas observed for EC1788, as evidenced by test animal total body weight;however, test animal total body weight increased after the last dosingday.

EXAMPLE. EC1879 in vivo activity against tumors. As shown in FIG. 4,EC1879 (▴) dosed at 2 μmol/kg TIW for two weeks decreases KB tumors intest animals compared to untreated control (▪). Moreover, EC1879 gave acomplete response in 5/5 test animals, and cure in 5/5 test animals.Toxicity was not observed for EC1879, as evidenced by test animal totalbody weight.

METHOD EXAMPLE. TNBC Tumor Assay. Triple negative breast cancer (TNBC)is a subtype characterized by lack of gene expression for estrogen,progesterone and Her2/neu. TNBC is difficult to treat, and the resultingdeath rate in patients is reportedly disproportionately higher than forany other subtype of breast cancer. A TNBC xenograft model was generatedin an analogous way to the KB and M109 models described herein byimplanting MDA-MB-231 breast cancer cells in nu/nu mice. Dosing wasinitiated when the s.c. tumors had an average volume between 110-150(generally 130) mm³ (to), typically 17 days post tumor inoculation(PTI). Test animals (5/group) were injected intravenously, generallythree times a week (TIW), for 2-3 weeks with varying doses, such as with1 μmol/kg to 5 mol/kg, of the drug delivery conjugate or with anequivalent dose volume of PBS (control), unless otherwise indicated.Dosing solutions were prepared fresh each day in PBS and administeredthrough the lateral tail vein of the mice.

EXAMPLE. EC1744 in vivo activity against tumors. As shown in FIG. 5,EC1744 (♦) dosed at 2 μmol/kg TIW for two weeks decreased triplenegative breast cancer (TNBC) MDA-MB-231 tumors in test animals comparedto untreated control (▪). Moreover, EC1744 gave a complete response in5/5 test animals, and cure in 4/5 test animals. Toxicity was notobserved for EC1744, as evidenced by test animal total body weight.

METHOD. Human cisplatin-resistant cell line. A human cisplatin-resistantcell line was created by culturing FR-positive KB cells in the presenceof increasing cisplatin concentrations (100→2000 nM; over a >12 monthperiod). The cisplatin-resistant cells, labeled as KB-CR2000 cells, werefound to be tumorigenic, and were found to retain their FR expressionstatus in vivo. KB-CR2000 tumors were confirmed to be resistant tocisplatin therapy. Treatment with a high, toxic dose of cisplatin(average weight loss of 10.3%) did not produce even a single partialresponse (PR).

METHOD. Human serum stability. Conjugates described herein may be testedin human serum for stability using conventional protocols and methods.The test compound may be administered to the test animal, such as bysubcutaneous injection. The plasma concentration of the conjugate, andoptionally one or more metabolites, may be monitored over time. Theresults may be graphed to determine Cmax, Tmax, half-life, and AUC forthe test compound and metabolites.

METHOD. Plasma clearance. In vivo studies include a minimum of 3 testanimals, such as rats, per time point. Illustratively, female Lewis ratswith jugular vein catheters (Harlan, regular rodent diet) may be given asingle subcutaneous injection of test compound. Whole blood samples (300μL) may collected at the following time points: 1 min, 10 min, 30 min, 1h, 2 h, 3 h, 4 h, 8 h, and 12 h after injection. The blood samples maybe placed into anti-coagulant tubes containing 1.7 mg/mL of K₃-EDTA and0.35 mg/mL of N-maleoyl-beta-alanine (0.35 mg/mL) in a 0.15% acetic acidsolution. Plasma samples may be obtained by centrifugation for 3 min at˜2,000 g and stored at −80° C. The amounts of test compound in theplasma and any metabolites were quantified by LC-MS/MS.

1.-50. (canceled)
 51. A compound of the formula

wherein R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a),R^(10a), R^(2c), R^(3c), R^(4c), R^(5c) are H; and L⁵ is selected fromthe group consisting of C₁-C₁₀ alkyl, —(CR⁴⁹═CR^(49′))_(u)—,—(CR⁴⁹R^(49′))_(u)C(O)—, —CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— and—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹and R^(49′) is independently selected from the group consisting of H, D,C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, whereineach hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl andC₃-C₆ cycloalkyl is independently optionally substituted by halogen,C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl,—OR⁵⁰, —OC(O)R⁵⁰, —OC(O)NR⁵⁰R^(50′), —OS(O)R⁵⁰, —OS(O)₂R⁵⁰, —SR⁵⁰,—S(O)R⁵⁰, —S(O)₂R⁵⁰, —S(O)NR⁵⁰R^(50′), —S(O)₂NR⁵⁰R^(50′),—OS(O)NR⁵⁰R^(50′), —OS(O)₂NR⁵⁰R^(50′), —NR⁵⁰R^(50′), —NR⁵⁰C(O)R⁵¹,—NR⁵⁰C(O)OR⁵¹, —NR⁵⁰C(O)NR⁵¹R^(51′), —NR⁵⁰S(O)R⁵¹, —NR⁵⁰S(O)₂R⁵¹,—NR⁵⁰S(O)NR⁵¹R^(51′), —NR⁵⁰S(O)₂NR⁵¹R^(51′), —C(O)R⁵⁰, —C(O)OR⁵⁰ or—C(O)NR⁵⁰R^(50′); R⁵⁰, R^(50′), R⁵¹ and R^(51′) are each independentlyselected from the group consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl,C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl and 5- to 7-membered heteroaryl; u is in each instance 0, 1,2, 3, 4 or 5, or a pharmaceutically acceptable salt thereof.
 52. Thecompound of claim 51, or a pharmaceutically acceptable salt thereof,wherein L⁵ is C₁-C₁₀ alkyl or —(CR⁴⁹R^(49′))_(u)C(O)—, each R⁴⁹ andR^(49′) is H, and u is 1, 2, 3, or 4; or a pharmaceutically acceptablesalt thereof.
 53. A compound of the formula

wherein, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a)and R^(10a) are H; and L⁵ is selected from the group consisting ofC₁-C₁₀ alkyl, —(CR⁴⁹═CR^(49′))_(u)—, —(CR⁴⁹R^(49′))_(u)C(O)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)—,—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′))_(u)C(O)— and—CH₂CH₂(OCR⁴⁹R^(49′)CR⁴⁹R^(49′)CR^(49′))_(u)C(O)—, wherein each R⁴⁹ andR^(49′) is independently selected from the group consisting of H, D,C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl and C₃-C₆ cycloalkyl, whereineach hydrogen atom in C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl andC₃-C₆ cycloalkyl is independently optionally substituted by halogen,C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆ alkynyl, C₃-C₆ cycloalkyl, 3- to7-membered heterocycloalkyl, C₆-C₁₀ aryl, 5- to 7-membered heteroaryl,—OR⁵⁰, —OC(O)R⁵⁰, —OC(O)NR⁵⁰R^(50′), —OS(O)R⁵⁰, —OS(O)₂R⁵⁰, —SR⁵⁰,—S(O)R⁵⁰, —S(O)₂R⁵⁰, —S(O)NR⁵⁰R^(50′), —S(O)₂NR⁵⁰R^(50′),—OS(O)NR⁵⁰R^(50′), —OS(O)₂NR⁵⁰R^(50′), —NR⁵⁰R^(50′), —NR⁵⁰C(O)R⁵¹,—NR⁵⁰C(O)OR⁵¹, —NR⁵⁰C(O)NR⁵¹R^(51′), —NR⁵⁰S(O)R⁵¹, —NR⁵⁰S(O)₂R⁵¹,—NR⁵⁰S(O)NR⁵¹R^(51′), —NR⁵⁰S(O)₂NR⁵¹R^(51′), —C(O)R⁵⁰, —C(O)OR⁵⁰ or—C(O)NR⁵⁰R^(50′); R⁵⁰, R^(50′), R⁵¹ and R^(51′) are each independentlyselected from the group consisting of H, D, C₁-C₇ alkyl, C₂-C₇ alkenyl,C₂-C₇ alkynyl, C₃-C₆ cycloalkyl, 3- to 7-membered heterocycloalkyl,C₆-C₁₀ aryl and 5- to 7-membered heteroaryl; u is in each instance 0, 1,2, 3, 4 or 5, or a pharmaceutically acceptable salt thereof.
 54. Thecompound of claim 53, wherein, L⁵ is C₁-C₁₀ alkyl or—(CR⁴⁹R^(49′))_(u)C(O)—, wherein each R⁴⁹ and R^(49′) is H, and u is 1,2, 3, 4 or 5; or a pharmaceutically acceptable salt thereof.
 55. Acompound of the formula

wherein, R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a),R^(10a) and R^(1e) are H; or a pharmaceutically acceptable salt thereof.56. The compound of claim 55, or a pharmaceutically acceptable saltthereof, wherein L⁵ is C₁-C₁₀ alkyl or —(CR⁴⁹R^(49′))_(u)C(O)—, each R⁴⁹and R^(49′) is H, and u is 1, 2, 3, or 4; or a pharmaceuticallyacceptable salt thereof.
 57. A compound of the formula

wherein R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a),R^(10a), R^(1d) are H; or a pharmaceutically acceptable salt thereof.58. The compound of claim 57, or a pharmaceutically acceptable saltthereof, wherein L⁵ is C₁-C₁₀ alkyl or —(CR⁴⁹R^(49′))_(u)C(O)—, each R⁴⁹and R^(49′) is H, and u is 1, 2, 3, or 4; or a pharmaceuticallyacceptable salt thereof.
 59. A compound of the formula

wherein R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a)and R^(10a) are H; or a pharmaceutically acceptable salt thereof. 60.The compound of claim 59, or a pharmaceutically acceptable salt thereof,wherein L⁵ is C₁-C₁₀ alkyl or —(CR⁴⁹R^(49′))_(u)C(O)—, each R⁴⁹ andR^(49′) is H, and u is 1, 2, 3, or 4; or a pharmaceutically acceptablesalt thereof.
 61. A compound of the formula

wherein R^(2a), R^(3a), R^(4a), R^(5a), R^(6a), R^(7a), R^(8a), R^(9a)and R^(10a) are H; or a pharmaceutically acceptable salt thereof. 62.The compound of claim 61, or a pharmaceutically acceptable salt thereof,wherein L⁵ is C₁-C₁₀ alkyl or —(CR⁴⁹R^(49′))_(u)C(O)—, each R⁴⁹ andR^(49′) is H, and u is 1, 2, 3, or 4; or a pharmaceutically acceptablesalt thereof.